FABRICATION AND ANALYSIS OF (ALUMINIUM-INORGANIC MATERIAL) METAL MATRIX COMPOSITES USING STIR CASTING METHOD
A Project Report
In Partial Fulfillment of the
Requirements for the degree of
Bachelor of Technology (B. Tech.)
Anubhav Verma (1402940028) Harsh Pundir (1402940063)
Aakash Mishra (1502940901) Alok Porwal (1402940017)
Under the Supervision
Prof. Kumari Archana
KIET GROUP OF INSTITUTIONS GHAZIABAD
DR. A.P.J. ABDUL KALAM TECHNICAL UNIVERSITY,
LUCKNOW, UTTAR PRADESH, MAY’ 2018
This is to certify that Project Report entitled “FABRICATION AND ANALYSIS OF (ALUMINIUM-INORGANIC MATERIAL) METAL MATRIX COMPOSITES” which is submitted by Anubhav Verma, Aakash Mishra, Harsh Pundir, Alok Porwal in Partial fulfillment of the requirement for the award of degree Bachelor of Technology, Ghaziabad of Uttar Pradesh Technical University, Lucknow, is a record of supervision. The matter embodied in this thesis is original and has not been submitted by for the award of any other degree.
Date: Supervisor :
Prof. Kumari Archana
Metal matrix composites (MMCs) have a significantly improved properties such as high specific strength, specific modulus, damping capacity and high wear resistance compared to other reinforced alloys. There is the reason for more interest in composites containing low density and low cost reinforcements. Among various discontinuous occur in alloy used, graphite is one of the most inexpensive and low density reinforcement material available in large scale as solid waste by-product during combustion of coal in the utilization at various thermal power plants. Hence, composites with graphite as reinforcement are likely to reduced the cost effect for wide spread applications in automotive and small engine applications. Now a days the particulate reinforced material as aluminium matrix composite are gaining importance in the market because of their low cost with advantages like micro structural properties and the possibility of Secondary processing facilitating fabrication of secondary various components. The present research has been focused on the utilization of large quantity available of graphite in useful manner by dispersing it into aluminium to produce composites by stir casting method. In current project work, the casting of three designed composites are being done yet. In Composites, Aluminium is used as base metal while graphite used as reinforcements. Fabrication is done by the use of stir casting method of casting which is most likely to be uused in now a days. After that mechanical testing is also being done on the same fabricated composition, i.e., Rockwell Hardness test, Tensile test on Programmable UTM. On the basis of thechange in results of mechanical testing, different conclusions are made.
It gives us a great immense pleasure to present our report of the B. Tech Project which is undertake during B. Tech Final Year. We give special thanks to Assistant Professor , Ms. Kumari Archana, Department of Mechanical Engineering, at Krishna Institute of
Engineering ; Technology, Ghaziabad for his important support and guidance throughout the course of our work. His Support, kindness and hard work regarding our project work have been a constant source of inspiration for us. It is only his incomparable efforts that our project success have been seen light of the day. We also take the pleasure to acknowledge the important contribution of Dr. K.L.A. Khan, Head of Mechanical Engineering department, Krishna Institute of Engineering ; Technology, Ghaziabad for his full support and assistance during the working of the project. We also do not like to left the opportunity of to acknowledge the contribution of all supportive faculty members of the mechanical department for their kind support and important cooperation during the work of our project.
We would also consider like to be thank Mr. Surendra Kumar, and Mr. Charanjeet Kumar, Lab Instructor in department , Mr. Noor Muhamad, Mr. Suresh Kumar and Mr. Mantu Kumar Singh, Lab Assistant, Krishna Institute of Engineering ; Technology, Ghaziabad for their full support and cooperation during work of project. And last but not the least, we acknowledged our supportive friends for their important contribution in the completion of our project.
Name: Anubhav Verma Name: Aakash Mishra
Roll No: 1402940028 Roll No: 1502940901
Name: Harsh Pundir Name: Alok Porwal
Roll No: 1402940063 Roll No: 1402940017
TABLE OF CONTENTS
Titles/Subtitles Page No.
Table list 7
Figures list 8
Symbols, Abbreviations, Nomenclature list 9
1.1 Aluminium 10
1.2 Properties of Aluminium 10
Applications of Aluminium 13
1.4 Aluminium Alloys 16
1.5 Designation of Aluminium 18
1.6 Wrought Alloys 19
1.7 Cast Alloys 20
Metal Matrix Composites 22
Literature Survey 24-27
3.1 Solid State Method 28
3.2 Liquid State Method 28
3.3 Stir Casting Method of fabrication of MMC’s 28
3.4 Stir Casting 29
3.6 Why Graphite ? 32
3.7 Interfacial Parameters 32
3.8 Criteria which are important in considering the interface that exists in an MMC material 33
3.9 Points to remember 36
3.10 Mechanical Testing 36
3.11 Equipment Specifications 48
3.12 Project Snaps 49
Results and Discussion 54-58
4.1 Mechanical Test Report – Al 6061 54
4.2 Mechanical Test Report – Al 6061+2% graphite 55
Mechanical Test Report – Al 6061+4%graphite 56
4.4 Mechanical Test Report -Al 6061+6% graphite 57
4.5 Brinells Hardness Test 58
4.6 Vickers Hardness Test 58
5.1 Tensile Testing 59
5.2 Hardness Testing 60
List of Tables
Table No. Title Page No.
1.1 Chemical Properties of Aluminium 12
1.2 Physical Properties of Aluminium 12
1.3 Mechanical Properties of Aluminium 13
1.4 Designation of Aluminium 20
1.5 Common Aluminium alloys and their applications 21
4.1 Brinells Hardness Testing 58
4.2 Vickers Hardness Testing 58
List of Figures
Figure No. Title Page No.
3.1 Stir Casting Set Up (Line Diagram) 30
3.2 Stir Casting Set Up (Actual) 30
3.3 Liquid drop on a solid surface 34
3.4 Schematic diagram of setup of tensile test 37
3.5 Computerized UTM 38
3.6 Shape of specimen of UTM 39
3.7 Engineering stress strain curve 40
3.8 Vickers hardness test 47
3.9 Shape of indenter for different hardness tests 47
3.10 Mould Pattern (front view) 49
3.11 Mould Pattern (side view) 50
3.12 Mould Preparation 50
3.13 Melting process in furnace 51
3.14 Pouring molten metal to mould 52
3.15 UTM Specimen 52
3.16 Vickers hardness test specimen 53
3.17 Brinells hardness test specimen 53
4.1 Mechanical test report-Al 6061 54
4.2 Mechanical test report-Al 6061+2%graphite 55
4.3 Mechanical test report-Al 6061+4%graphite 56
4.4 Mechanical test report-Al 6061+6%graphite 57
5.1 Graph showing variation in tensile strength of different compositions 59
5.2 Graph showing variation in hardness of different compositions 60
List of Symbols
E : Young’s Modulus
?m : Micro metre
pm : Pico metre
Ø : Contact angle
HRB : Rockwell Hardness Number on B scale
%El : Percentage Elongation
%RA : Percentage reduction in area
Ao : Cross sectional Area of the gauge
Af : Area at the time of failure
N : Average number of grains
n : Grain Size Number
Aluminium element ,whose symbol Al, is the most resourceful metallic element in the Earth.
The Aluminium atomic number is 13. And this element is present in group 3 of the periodic table of the element. Pure form of the Aluminium element has the face centered cubic crystal structure at the micro structure level. At the initial stage aluminium is found in bauxite ore. Pure form of aluminium element is very soft in nature, has the silvery colour, and possess the high electrical conductivity. Aluminium is a very light metal in weight with a specific weight around the 2699kg/m3, which is very less as compared to the steel. For example, if we used aluminium material for the manufacturing of the vehicle it is become very light in nature and the dead weight is also very light, and side by side it increasing load capacity. Its strength and the surface property are improved by the various thermal heat processes and the various heat treatment processes. Aluminium is used to generates a protective oxide layer of coating and is highly corrosive resistant property. There are various heat treatment processes such as anodizing, painting can be used to improve its property. Aluminium material is very good conductor of heat and electricity and its conductive property is good as the copper and its advantage is its light weight that’s the reason of the selection of the aluminium for the use of its as the transmission line for the supply of the electricity . it is also used as the good reflector of the visible light and that’s the reason it use as the layer formation on outside of the heating wall. Aluminium is ductile material in nature and has a considerable low melting point and density value as compared to the other. And its advantage is that In a molten condition it can be processed in a number of way for the fabrication of the different type of the product. Its ductile property of Aluminium is allow it to be basically formed close to the end of the other products of design. Aluminium foil are present in market are formed due to that property, even when its rolled to only 0.006 mm thickness, is still very useful property of aluminium to be rolled in thin wire and in the thin sheet. Moreover, the aluminium material is non toxic in nature and has the very slurry taste substances. Which make it very useful for the food oreservation for packaging of the food, sensitive products. Aluminium material is 100% recyclable tendency with no compromise in the qualities of the product life and the material itself. The re-melting of Aluminium required little energy: only about 5% the energy required to produce the primary metal initially is needed in the recycling process.
1.2. Properties of Aluminium
After the iron form of the metal , aluminium is the second most widely used metal in the world. The properties of aluminium includes: low density and low weight, high strength, malleability, easy machining, excellent corrosion resistance and good thermal and electrical conductivity are aluminium most important properties. Aluminium is also very easy to recycle as compared to the other material.
One of the best known properties of aluminium is that it is light, with a density one third that of steel, 2.699 kg/m3. The low density of aluminium accounts for it being lightweight but this
does not affect its strength.
Aluminium alloys commonly have tensile strengths of between 60 and 710 MPa. The range for alloys used is 140 – 310 MPa. Unlike most steel grades material, aluminium does not
Change its property o brittleness at low temperatures. And its strength increases, At high temperatures,
aluminium’s strength decreases. At temperatures continuously above 100°C, strength is affected to the extent that the weakening must be taken into account.
1.2.3 Linear expansion
Compared with other metals, aluminium has a relatively large coefficient of linear expansion.
This has to be taken into account in some designs.
It is very easy to machine the aluminium material by the different methods such as the – milling, drilling, cutting, punching, bending, etc. Furthermore, the energy consumption is very much low as compared to the other method.
Aluminium’s superior malleability is essential for extrusion. With the metal either hot or cold, this property is also exploited in the rolling of strips and foils, as well as in bending and other forming operations. Such as the formation of the concept is very useful.
Aluminium is a good conductor of heat and electricity. An aluminium conductor weight is very low as compared to the other material which has the same conductive property.
Features facilitating easy jointing are often incorporated into profile design. Fusion welding,
Friction Stir Welding, bonding and taping are also used for joining.
Another of the properties of aluminium is that it is a good reflector of both visible light and
1.2.9 Screening EMC
Tight aluminium boxes can effectively exclude or screen off electromagnetic radiation. The
better the conductivity of a material, the better the shielding qualities.
1.2.10 Corrosion resistance
Aluminium is going to reacts with the oxygen in the nature to form an considerable thin layer of oxides. This layer is very ense in nature and provide the excellent corrosion protection for the material. The layer having the self-repairing property if damaged by the corrosion. Anodizing heat treatment process increases the thickness of the oxide layer form on the surface and thus improves the strength of the natural corrosion protection of the surface if the material. Where aluminium is used household goods and utensils, thicknesses of between 14 and 24 ?m are common. Aluminium is extremely durable in nature and slightly very compatible ..
1.2.11 Non-magnetic material
Aluminium is a non-magnetic (actually paramagnetic) material. To avoid interference of
magnetic fields aluminium is often used in magnet X-ray device.
1.2.12 Zero toxicity
After oxygen and silicon, aluminium is the most common element in the Earth’s crust.
Aluminium compounds also occur naturally in our food.
Number ,symbol ,name 13, Al, Aluminium
Block, period, group P ,3, 13
Crystal Structure Face Centered Cubic
Atomic Mass 26.98153 g/mole
Electronic Configuration Ne 3S2 3P1
Electron per shell 2, 8, 3
1.2.13 Physical Properties :
Density 2700 kg/m3
Liquid Density 2375 kg/m3
Melting Point 660.32oC
Boiling Point 2519oC
Heat of Fusion 10.71 KJ/mol
Heat of Vaporization 294 KJ/mol
Heat Capacity 24.20 J/mol K
Electrical Resistivity (20oC) 26.50 ?m
Thermal Conductivity 237 W/mK
Thermal Expansion (25oC) 23.1 Hm/K
Speed of Sound (thin rod) 5000m/sec
Young’s Modulus 70 GPa
Shear Modulus 26 GPa
Bulk Modulus 76 GPa
Possion Ratio 0.35
Vicker’s hardness number 167
Brinell’s hardness number 245
1.3 Applications of Aluminium:
Electrical Conductors manufactured
Building and Architecture
High Pressure Gas Cylinders shells
Ladders and Access Equipment
Road Barriers and Signs
Domestic and Office Furniture
1.3.1 Electrical Conductors:
It is very good in conductive nature if the electricity and its alloy are also good such as the series of the 6000 ; 7000 both series alloy are good.
A very large overhead transmission line of the electricity lines are used aluminium as the conductive material in place of the copper. The strength of the aluminium is the advantage to be selected as the conductor of the transmission .
Aluminium alloys have a conductivity average in the range of the 59% of the International Annealed Copper Standard (IACS) but just because of the its density its carry more current as compare to the copper material.
Aluminium and its alloys are the primary choice of the manufacturing the auto parts and the fabrication of the aero space part.
Even yet the total manufacturing capacity of the industry are consider the aluminium alloy for its manufacturing and it can be cover as the 69% of the market of the manufacturing industry. The combination of different property such as the light weight, low cost, high strength, corrosion resistant, low density are the prime concern for the selection of the aluminium as the fabrication material . There are now very many examples of its use in commercial vessels, rail cars both passenger and freight, marine hulls and superstructures and military vessels.
Rate of car production in now a day includes aluminium as the main material as fabricate the engine castings, wheels, radiators and increasingly as body parts. For general production the 6000 and 7000 series alloys provide the good strength and has the good corrosion resistance, high rate of toughness and easiness of welding. In aircraft the very strong 6000, 7000 series alloys are preferred, and in military vessels and the ammunition the good weld ability 6000 series alloys can provide ballistic properties to match steel armor of the military .
The main use of the 6000 series alloys as foil manufacturing for food wrapping and for containers utilized for their good corrosion resistance and preventive properties against UV light and other effective radiation , moisture . Foil can be basically formed, good decorated and can be usefully combined with paper and plastic if required of the coating.
The most common use of the aluminium is to make the beverages cans to store the food item to prevent it from the external source of the demages. This has rapidly grown to some 16% of all aluminium consumption; one hundred thousand million cans a year in the India itself.
Cans for some food products such as the , fish, which is very easy opening facilities of aluminium, have been used for over seventy years. From a easiness point of view there is no other reason why more we use of aluminium as a can material, to less costs seem to be the restraining factor. This may become more important in the future, see the section on recycling.
1.3.4 Building and Architecture:
Aluminium is used in buildings material for a wide range of construction of applications. These include roofing for factories , roof formation, doors the houses, windows, and many other things which can be come in the light of the construction of the house by the application of the aluminium.
Aluminium structures and cladding are done on the various items of the ancient things which comes at the end of the life in now a days and its damaging factor are come in light and its damaging reasons also .
In building applications of aluminium material the durability property of aluminum is have the most important factor to be considered. There are a number of good examples of the durability property of aluminium which may be various monuments present in various location of the world which has the good example of the aluminium good property. More recently the oil and gas industry has employed aluminium widely in use structures making.
The 6000 and 7000 series alloys will perform various performance, with no reduction of its strength, without protection in industrial. They may however suffer some deterioration in their appearance and protection by painting or anodizing can be advisable.
Anodized film coating is used to prevent the outer surface color from the external atmosphere of the aluminium product which is utilized to make the effort for the wide application in the making of the product by its alloys.
These finishing operations may also, be done by its alloy to get the good surface property and the bright surface finidh.
1.3.5 Miscellaneous Applications:
The applications discussed above have the utilization of the 80 % of the aluminium availability in the fabrication of the product and the remaining of the 20 % of the use of the applications.
1.3.6 High Pressure Gas Cylinders:
Compressed gas cylinders with having the high pressure gas storage shells are used to be manufactured and the high pressure gas to be transport by that shell which has the high strength and those gases like CO2, H2, etc are the examples of the gas.
1.3.7 Machined Components:
Which one has the high tolerance can be machined from the 6000 and 7000 series alloys.
These alloys have additions of lead which gives them good machine ability that approaches that of good finish.
1.3.8 Ladders and Access Equipment:
Aluminium alloys are highly suitable material to manufactured ladders and access equipment due to their lightweight, corrosion resistance and toughness property. The 6000 series are used.
1.3.9 Sporting Goods:
The 7000 and 6000 series alloys are used for golf clubs and trolleys equipment, racquets for many sports things, snooker and pool, often employing spin off from aerospace technology.
1.3.10 Road Barriers and Signs:
Extrusion part and roll formed sheet in the 6000 and 7000 series alloys provide good corrosion resistance and decorative ability.
1.3.11 Domestic and Office Furniture:
The complex shape and surface finish of extrusions part in the 6000 series alloys coupled with the other form of the material which has to be extrude and weld with that aluminium material.
1.4. Aluminium Alloys
Aluminium alloys are alloys in which aluminium (Al) is the predominant metal. The typical alloying elements are copper, magnesium, manganese, silicon, tin and zinc. There are two principal classifications of aluminium, namely casting alloys and wrought alloys, both of which are further subdivided into the categories which are heat-treatable and non-heat-treatable. Now a days about 85% of aluminium is used for wrought products, for example rolled plate, foils and extrusions. Cast aluminium alloys yield cost-effective products due to the low melting point, although they generally have lower tensile strengths than wrought alloys. The most important cast aluminium alloy system is Al–Si, where the high levels of silicon (4.0–13%) contribute to give good casting characteristics. Aluminium alloys are widely used in engineering structures and components where light weight or corrosion resistance is required.
Alloys composed mostly of aluminium have been very important in aerospace manufacturing since the introduction of metal skinned aircraft. Aluminium-magnesium alloys are both lighter than other aluminium alloys and much less flammable than alloys that contain a very high percentage of magnesium. Aluminium alloy surfaces will formulate a white, protective layer of corrosion aluminium oxide if left unprotected by anodizing and/or correct painting procedures. In a wet environment, galvanic corrosion can occur when an aluminium alloy is placed in electrical contact with other metals with more negative corrosion potentials than
aluminium, and an electrolyte is present that allows ion exchange. Referred to as dissimilar metal corrosion this process can occur as exfoliation or inter-granular corrosion. Aluminium alloys can be improperly heat treated. This causes internal element separation and the metal corrodes from the inside out. Aircraft mechanics deal daily with aluminium alloy corrosion.
1.4.2 Engineering use and aluminium alloys properties:
Aluminium with a wide range of properties are used in engineering structures manufactured . Alloy systems are classified by a number system (ANSI) .Selecting the right alloy of the aluminium for a given application entity according to the different point of considerations of its tensile strength, density, ductility, formability, Workability, weld ability, and corrosion resistance, to name a few. A brief historical overview of alloys and manufacturing technologies is given in Ref.4 Aluminium alloys are used most in the aerospace and in aircraft due to their high strength-to-weight ratio. On the other hand of that, pure aluminium metal is much too soft for such uses, and it does not have the high tensile strength that is needed for airplanes and helicopters.
188.8.131.52 Aluminium alloys versus types of steel:
Aluminium alloys typically have an elastic modulus of about 70 GPA, which is About one-third of the elastic modulus of most kinds of steel and steel alloys. Therefore, for a given load, a component or unit made of an aluminium alloy will experience a greater deformation in the elastic regime than a steel part of the identical size and shape. Though there are aluminium alloys with some-what-higher tensile strengths than the commonly used kinds of steel, simply replacing a steel part with an aluminium alloy might lead to problems. With completely new metal products, the design choices are often governed by the choice of manufacturing technology. Extrusions are particularly important in this regard, owing to the ease with which aluminium alloys, particularly the Al–Mg–Si series, can be extruded to form complex profiles. In general, stiffer and lighter designs can be achieved with aluminium alloys than is feasible with steels. For instance, consider the bending of a thin-walled tube: the second moment of area is inversely related to the stress in the tube wall, i.e. stresses are
lower for larger values. The second moment of area is proportional to the cube of the radius times the wall thickness, thus increasing the radius (and weight) by 26% will lead to a halving of the wall stress. For this reason, bicycle frames made of aluminium alloys make use of larger tube diameters than steel or titanium in order to yield the desired stiffness and strength. In automotive engineering, cars made of aluminium alloys employ space frames made of extruded profiles to ensure rigidity. This represents a radical change from the common approach for current steel car design, which depends on the body shells for stiffness, known as unibody design. Aluminium alloys are widely used in automotive engines, particularly in cylinder blocks and crankcases due to the weight savings that are possible. Since aluminium alloys are susceptible to warping at elevated temperatures, the cooling system of such engines is critical. Manufacturing techniques and metallurgical advancements have also been instrumental for the successful application in automotive engines. In the 1960s, the aluminium cylinder heads of the Corvair earned a reputation. For failure and stripping of threads, which is not seen in current aluminium cylinder heads.
An important structural limitation of aluminium alloys is their lower fatigue strength compared to steel. In controlled laboratory conditions, steels display a fatigue limit, which is the stress amplitude below which no failures occur – the metal does not continue to weaken with extended stress cycles. Aluminium alloys do not have this lower fatigue limit and will continue to weaken with continued stress cycles. Aluminium alloys are therefore sparsely used in parts that require high fatigue strength in the high cycle regime (more than 107 stress cycles).
184.108.40.206 Heat sensitivity considerations:
Often, the metal’s sensitivity to heat must also be considered. Even a relatively routine workshop procedure involving heating is complicated by the fact that aluminium, unlike steel, will melt without first glowing red. Forming operations where a blow torch is used can reverse or remove heat treating, therefore is not advised whatsoever. No visual signs reveal how the material is internally damaged. Much like welding heat treated, high strength link chain, all strength is now lost by heat of the torch. The chain is dangerous and must be discarded. Aluminium also is subject to internal stresses and strains when it is overheated;
the tendency of the metal to creep under these stresses tends to result in delayed distortions. For example, the warping or cracking of overheated aluminium automobile cylinder heads is commonly observed, sometimes years later, as is the tendency of improperly welded aluminium bicycle frames to gradually twist out of alignment from the stresses of the welding process. Thus, the aerospace industry avoids heat altogether by joining parts with rivets of like metal composition, other fasteners, or adhesives. Stresses in overheated aluminium can be relieved by heat-treating the parts in an oven and gradually cooling it—in effect annealing the stresses. Yet these parts may still become distorted, so that heat-treating of welded bicycle frames, for instance, can result in a significant fraction becoming misaligned. If the misalignment is not too severe, the cooled parts may be bent into alignment. Of course, if the frame is properly designed for rigidity, that bending will require enormous force.
Aluminium’s intolerance to high temperatures has not precluded its use in rocketry; even for use in constructing combustion chambers where gases can reach 3500 K. the Agena upper stage engine used a generatively cooled aluminium design for some parts of the nozzle, including the thermally critical throat region; In fact the extremely high thermal conductivity of aluminium prevented the throat from reaching the melting point even under massive heat flux, resulting in a reliable lightweight component. Because of its high conductivity and relatively low price compared with copper in the 1960s, aluminium was introduced at that time for household electrical wiring in North America, even though many fixtures had not been designed to accept aluminium wire. Galvanic corrosion from the dissimilar metals increases the electrical resistance of the connection. All of this resulted in overheated and loose connections, and this in turn resulted in some fires. Builders then became wary of using the wire, and many jurisdictions outlawed its use in very small sizes, in new construction. Yet newer fixtures eventually were introduced with connections designed to avoid loosening and overheating. At first they were marked “Al/Cu”, but they now bear a “CO/ALR” coding. Another way to forestall the heating problem is to crimp the aluminium wire to a short “pigtail” of copper wire. A properly done high-pressure crimp by the proper tool is tight enough to reduce any thermal expansion of the aluminium.
1.5 Designations of Aluminium:
1.5.1 Alloy designations:
Wrought and cast aluminium alloys use different identification systems.
Wrought aluminium is identified with a four digit number which identifies the alloying elements. Cast aluminium alloys use a four to five digit number with a decimal point. The digit in the hundreds place indicates the alloying Elements, while the digit after the decimal point indicates the form (cast shape or ingot).
1.5.2 Temper designation:
The temper designation follows the cast or wrought designation number with a dash, a
letter, and potentially a one to three digit number, e.g. 6061-T6. The definitions for the
F : As fabricated
H : Strain hardened (cold worked) with or without thermal treatment
H1 : Strain hardened without thermal treatment
H2 : Strain hardened and partially annealed
H3 : Strain hardened and stabilized by low temperature heating
A second digit denotes the degree of hardness
HX2= 1/4 hard
HX4= 1/2 hard
HX6= 3/4 hard
HX8= full hard
HX9= extra hard
O : Full soft (annealed)
T : Heat treated to produce stable tempers
T1 : Cooled from hot working and naturally aged (at room temperature)
T2 : Cooled from hot working, cold-worked and naturally aged
T3 : Solution heat treated and cold worked
T4 : Solution heat treated and naturally aged
T5 : Cooled from hot working and artificially aged (at elevated temperature)
T51 : Stress relieved by stretching
T510 : No further straightening after stretching
T511 : Minor straightening after stretching
T52 : Stress relieved by thermal treatment
T6 : Solution heat treated and artificially age.
Solution heat treated and stabilized
Solution heat treated, cold worked, and artificially aged
Solution heat treated, artificially aged, and cold worked
Cooled from hot working, cold-worked, and artificially
Note: W is a relatively soft intermediary designation that applies after heat treat and before
aging is completed.
The –W condition can be extended at extremely low temperatures but not indefinitely and
depending on the material will typically last no longer than 15 minutes at ambient
1.6 Wrought alloys:
The International Alloy Designation System is the most widely accepted naming scheme
for wrought alloys. Each alloy is given a four digit number, where the first digit indicates
the major alloying elements.
The most common aerospace alloys, but were susceptible to stress corrosion cracking and are increasingly replaced by 7000 series in new designs. 3000 series are alloyed with manganese, and can be work hardened. 4000 series are alloyed with silicon. They are also known as silumin. 5000 series are alloyed with magnesium. 6061 alloy is one of the most commonly used general purpose aluminium alloy.
1.6 Cast alloys:
The Aluminium Association (AA) has adopted a nomenclature similar to that of wrought alloys. British Standard and DIN have different designations. In the AA system, the second two digits reveal the minimum percentage of aluminium, e.g. 150.x corresponds to a minimum of 99.50% aluminium. The digit after the decimal point takes a value of 0 or 1, denoting casting and ingot respectively.
MAIN ALLOYING ELEMENTS
1XXX Minimum 99% aluminium
3XXX Silicon, Copper and/or magnesium
7XXX Zinc and Magnesium
9XXX Other Elements
Common Aluminium alloys and their applications
Aluminium alloy and Temper Typical Properties and Applications
1100-H14 Commercially pure aluminium resistant to chemical attack and weathering, low cost, ductile, easy to weld.
Used in chemical equipment, fan blades, sheet metal work
2014-T6, T651 Truck frames, aircraft structures, automotive parts, cylinders and pistons, machine parts, structural applications.
2017-T4, T451 Fasteners, fittings
Alclad High strength structural applications, excellent machinability in T-temper, fair workability, corrosion resistance. Used in trucks, automotive parts, screws and rivets.
3003-H16 Most popular general purpose alloy, stronger than 1100 with same good formability and weld ability. Used in cooking utensils, chemical equipment, pressure vessels, sheet metal work and storage tanks.
3004-H38 Sheet metal work, storage tanks, agricultural applications, building products, containers, electrical applications, furniture, trucks and trailers.
3150-H25 Sliding, sheet metal work, automotive parts, building products, electronics, furniture, trucks and trailers.
5005-H34 Appliances, utensils, architectural, electrical conductors, general sheet metal, hardware, marine applications.
5052-H34 Stronger than 3003, readily formable, good weld ability and resistance to corrosion, used in sheet metal work, hydraulic tube, appliances, pressure vessels, hardware signs, marine applications, trucks
1.8 Metal Matrix Composites (MMC’s)
Metal Matrix Composites are composed of a metallic matrix (Al, Mg, Fe, Cu Gr,etc.) and a formed ceramic (oxide, carbides) or metallic phase (Pb, Mo, W etc.). Ceramic reinforcement material may be silicon carbide, boron, alumina, silicon nitride, boron carbide, boron nitride etc. whereas Metallic Reinforcement may be used as tungsten, beryllium etc. MMCs are used for manufactured Space Shuttle, commercial airliners, electronic substrates, bicycles, automobiles, golf clubs and a variety of other applications. From the sense of material point of view tha metal matrix composites are basically used to manufactured, the advantages of MMCs lie in their retention of strength and stiffness at elevated temperature, good abrasion and creep resistance properties. Most MMCs are still in the development stage or the early stages of production and are not so widely established as polymer matrix composites. The main disadvantage of the metal matrix composites are high cost of fabrication, which has placed limitations on their actual applications. There are also advantages in some of the physical attributes of MMCs such as no significant moisture absorption properties, non-in flammability, low electrical and thermal conductivities and resistance to most radiations. MMCs have existed for the past 30 years and a wide range of MMCs have been studied.
Compared to monolithic metals, MMCs have:
Higher strength-to-density ratios
Higher stiffness-to-density ratios
Better fatigue resistance
Better elevated temperature properties o Higher strength
Lower creep rate
Lower coefficients of thermal expansion
Better wear resistance
The advantages of MMCs over polymer matrix composites are:
Higher temperature capability
Higher transverse stiffness and strength
No moisture absorption
Higher electrical and thermal conductivities
Better radiation resistance
No out gassing
Fabric ability of whisker and particulate-reinforced MMCs with
conventional metalworking equipment.
Some of the disadvantages of MMCs compared to monolithic metals and polymer matrix
Higher cost of some material systems
Relatively immature technology
Complex fabrication methods for fiber-reinforced systems (except for casting)
Limited service experience
Numerous combinations of matrices and reinforcements have been tried since work on MMC began in the late 1950s. However, MMC technology is still in the early stages of development, and other important systems undoubtedly will emerge. Numerous metals have been used as matrices. The most important have been aluminium, titanium, magnesium, and copper alloys and super alloys.
The most important MMC systems are:
Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide
Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide
Continuous fibers: silicon carbide, coated boron
Particulates: titanium carbide
Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particulates: silicon carbide, boron carbide, titanium carbide.
2. LITERATURE SURVEY
A.K. Jha, S.V. Prasad, G.S.Upadhaya
This article describes the dry sliding wear of 6061 aluminium alloy and composites containing up to 14 vol. % of graphite particle dispersions prepared by a power metallurgy route. Experiments were carried out with pin specimens against an EN25 steel disc using a pin-on-disc apparatus. The effects of varying sliding speed and distance, applied pressure and material characteristics, as well as the amount of graphite, on the dry sliding behaviour have been evaluated. The wear rates of the composites increased with increasing amounts of graphite. This anomalous behaviour has been attributed to the increased porosity (interconnected and interfacial) in the composites. SEM examination of the worn surfaces did not reveal the presence of graphite film on them. Most of the wear debris were flaky in nature.
L. Krishnamurthy, B.K. Sridhara, D. Abdul Budan
.Experiments were performed for fabrication of graphite based Al-6061 composite. Three
process variables stirrer speed of stirrer, pouring temperature of liquid phase and percentage of reinforcement (graphite) have been considered as input, however hardness in Vickers was taken to be output variable. It has been observed through experimental data that the hardness has non-linear relation with variables (graphite composition, Pouring temperature, Stirring speed). Hence attempt has been made to develop more accurate and computationally efficient
non-parametric approaches for the prediction of Hardness in Vickers. Using these experimental input-output data ANN based model is developed. The various parameters of ANN for experimental data are adjusted on trial and error basis to minimize MSE (Mean Squared error). The ANN based modeling approach is used for accurately predicting the hardness for all possible combinations of Graphite percentage, pouring temperature, stirring speed of stirrer, so that a suitable combination of these variables may be recommended to increase the hardness.
N. Radhika, B.S. Ghosh
As we done the heat treatment of graphite that taken from the thermal plant to reduce its moisture in the induction furnace. After it we have to melt the Al 6061 in the furnace having a capacity of 1000°C and then added preheated graphite into it .For increasing wet ability, we also added the Mg that means it decreases the surface tension of the graphite. For better mixing of all materials, a stirrer arrangement is adjusted which stirs the molted composite material. Also a Hexachloro-ethane tablet is using here to remove the slag from the molten MMC. After all of these, this molten material will be poured into the sand mould and fabricate the required shape of slab and rods.
S.A. Sajjadi, H.R. Ezatpour, M. Torabi Parizi
Metal–matrix composites (MMCs), as light and strong materials, are very attractive for application in different industries. In the present work, nano and micro-composites (A356/Al2O3) with different weight percent of particles were fabricated by two melt techniques such as stir-casting and compo-casting. Micro structural characterization was investigated by optical (OP) and scanning electron microscopy (SEM). Tensile, hardness and compression tests were carried out in order to identify mechanical properties of the composites. The results of micro structural study revealed uniform distribution, grain refinement and low porosity in micro and nano-composite specimens. The mechanical
results showed that the addition of alumina (micro and nano) led to the improvement in yield strength, ultimate tensile strength, compression strength and hardness. It was indicated that type of fabrication process and particle size were the effective factors influencing on the mechanical properties. Decreasing alumina particle size and using compo-casting process obtained the best mechanical properties.
N. Radhika, R. Subramanian , S. Venkat Prasat
Tribological behaviour of aluminium alloy (Al-Si10Mg) reinforced with alumina (9%) and graphite (3%) fabricated by stir casting process was investigated. The wear and frictional properties of the hybrid metal matrix composites was studied by performing dry sliding wear test using a pin-on-disc wear tester. Experiments were conducted based on the plan of experiments generated through Taguchi’s technique. A L27 Orthogonal array was selected for analysis of the data. Investigation to find the influence of applied load, sliding speed and sliding distance on wear rate, as well as the coefficient of friction during wearing process was carried out using ANOVA and regression equations for each response were developed. Objective of the model was chosen as ‘smaller the better’ characteristics to analyses the dry sliding wear resistance. Results show that sliding distance has the highest influence followed by load and sliding speed. Finally, confirmation tests were carried out to verify the experimental results and Scanning Electron Microscopic studies were done on the wear surfaces.
Muhammad Hayat Jokhio, Mukhtiar Ali Unar, Muhammad Ibrahim Panhwer
In the present study, high silicon content aluminium alloy–silicon carbide metal matrix composite material, with 10%SiC were successfully synthesized, using different stirring speeds and stirring times. The microstructure of the produced composites was examined by optical microscope and scanning electron microscope. The Brinell hardness test was performed on the composite specimens from base of the cast to top. The results revealed that stirring speed and stirring time influenced the microstructure and the hardness of composite. Microstructure analysis revealed that at lower stirring speed with lower stirring time, the particle clustering was more. Increase in stirring speed and stirring time resulted in better distribution of particles. The hardness test results also revealed that stirring speed and stirring time have their effect on the hardness of the composite. The uniform hardness values were achieved at 600 rpm with 10 min stirring. But beyond certain stir speed the properties degraded again. An attempt is made in this study to establish the trend between processing
parameters such as stirring speed and stirring time with microstructure and hardness of composite.
S.K. Biswas, B.N. Pramila Bai
Under lubricated conditions, Al-graphite particle composite is a good anti seizure bearing and antifriction material possessing properties which inhibit excessive temperature rise in bearings. The present study characterizes the dry wear properties of the composite. The dry wear characteristics of the Al-(2.7%–5.7% graphite particle) (50–200?m) composite were found to deteriorate with the addition of graphite, load and sliding distance. Both micro structural and microhardness studies of the worn sub surfaces and analysis of wear debris show that the reductions in strength and ductility of the composite due to graphite addition are the most likely causes of deterioration in the wear properties of the composite.
A.Baradeswaran, A. Elaya Perumal
This work investigates 7075 aluminium alloy–graphite composites for its tribological and mechanical behavior under dry sliding conditions. The conventional liquid casting technique was used for the fabrication of composite material and subjected to T6 heat treatment.
The reinforcement content was chosen as 5, 10, 15 and 20 wt. % of graphite to identify its potential for self-lubricating property under dry sliding conditions. Wear tests were conducted by using pin on disc apparatus to evaluate the tribological behavior of the composite and to determine the optimum content of graphite for its minimum wear rate.
The wear rate decreases with addition of graphite content and reaches its minimum at 5 wt.% graphite. The wear mass loss was found to decrease with increasing sliding distance. The average coefficient of friction decreases with addition of graphite content and was found to be minimum at 5 wt.% graphite. The mechanical properties of the composites and base alloy were tested. The mechanical properties decrease with increasing graphite content as compared to base alloy. The worn surfaces were examined through SEM. The presence of 5 wt.% graphite in the composites can exhibit superior wear property as compared to base alloy.
Andrew Mills, Mohammed Farid, J.R. Selman, Said AL-Hallaj
The thermal conductivity of paraffin wax was increased by two orders of magnitude by impregnating porous graphite matrices with the paraffin. The graphite matrices were fabricated by compacting flake graphite that had been soaked in a bath of sulfuric and nitric acid then heat-treated at 900 °C. The properties of the graphite matrix and paraffin phase change material (PCM) composites were measured for graphite matrix bulk densities ranging from 50 g/L to 350 g/L. The properties studied include the thermal conductivity in directions parallel and perpendicular to the direction of compaction, paraffin mass fraction, and the latent heat of fusion of the composite samples. The latent heat of fusion and phase change characteristics of the graphite/paraffin composites were studied using differential scanning calorimetry (DSC). Scanning electron microscope (SEM) pictures are included to visualize the morphology of the graphite during each stage of the composite fabrication process. The performance of the PCM-composite was demonstrated by using the PCM-composite as a passive thermal management system for a lithium ion battery pack discharged at high rates.
F. Akhlaghi, A. Zare-Bidaki
The influence of graphite content on the dry sliding and oil impregnated sliding wear
characteristics of sintered aluminum 2024 alloy–graphite (Al/Gr) composite materials has been assessed using a pin-on-disc wear test. The composites with 5–20 wt.% flake graphite particles were processed by in situ powder metallurgy technique. For comparison, compacts of the base alloy were made under the same consolidation processing applied for Al/Gr composites. The hardness of the sintered materials was measured using Brinell hardness tester and their bending strength was measured by three-point bending tests. Scanning electron microscopy (SEM) was used to analyze the debris, wear surfaces and fracture surfaces of samples. It was found that an increase in graphite content reduced the coefficient of friction for both dry and oil impregnated sliding, but this effect was more pronounced in dry sliding. Hardness and fracture toughness of composites decreased with increasing graphite content. In dry sliding, a marked transition from mild to severe wear was identified for the base alloy and composites. The transition load increased with graphite content due to the increased amount of released graphite detected on the wear surfaces. The wear rates for both dry and oil impregnated sliding were dependent upon graphite content in the alloy. In both cases, Al/Gr composites containing 5 wt.% graphite exhibited superior wear properties over the base alloy, whereas at higher graphite addition levels a complete reversal in the wear behavior was observed. The wear rate of the oil impregnated Al/Gr composites containing 10 wt. % or more graphite particles was higher than that of the base alloy. These observations were rationalized in terms of the graphite content in the Al/Gr composites which resulted in the variations of the mechanical properties together with formation and retention of the solid lubricating film on the dry and/or oil impregnated sliding surfaces.
Brij K. Dhindaw, Avijit Moitra
Directional solidification experiments in a Bridgman-type furnace were used to study particle behavior at the liquid/solid interface in aluminum metal matrix composites. Graphite or silicon carbide particles were first dispersed in aluminum-base alloys via a mechanically stirred vortex. Then, 100-mm-diameter and 120-mm-long samples were cast in steel dies and used for directional solidification. The processing variables controlled were the direction and velocity of solidification and the temperature gradient at the interface. The material variables monitored were the interface energy, the liquid/particle density difference, the particle/liquid thermal conductivity ratio, and the volume fraction of particles. These properties were changed by selecting combinations of particles (graphite or silicon carbide) and alloys (Al-Cu, Al-Mg, Al-Ni). A model which considers process thermodynamics, process kinetics (including the role of buoyant forces), and thermo physical properties was developed. Based on solidification direction and velocity, and on materials properties, four types of behavior were predicted. Sessile drop experiments were also used to determine some of the interface energies required in calculation with the proposed model. Experimental results compared favorably with model predictions.
Le Zhang, Wei Zhai, Lin Zhang
Aluminum/graphene (Al/G) composites with enhanced heat-dissipation and mechanical
properties were prepared by the powder metallurgy (P/M) technique. Grapheme was first
uniformly coated on the surface of micro-sized aluminum (Al) powders by an in-situ reduction reaction of GO and Al. Al/G bulk composites with uniform graphene dispersion in Al matrix were fabricated by the simple conventional P/M technique. Enhancements of 15.4% in thermal conductivity, 9.1% in specific heat capacity, 21.1% in hardness, and 25.6% in compressive strength were achieved with only 0.3 wt% grapheme addition into pure Al.
Vignesh Ganesan, Milon Selvam Dennison, Nelson A.J.R.
The present examination has been centered on the use of welding slag of electrode E6013 in a valuable way by scattering it into aluminium alloy Al6061 to produce a composite by stir casting technique. The mechanical property studied is the hardness of the produced composites. The experimental results showed significant changes in each composition. The hardness tend to increase when compared to the unreinforced Al6061.
Manufacturing and Forming Methods:
MMC manufacturing can be broken into three types, i.e. Solid, Liquid and Vapour.
3.1 Solid State Method:
Powder blending and consolidation (powder metallurgy): Powdered metal and discontinuous reinforcement are mixed and then bonded through a process of compaction, degassing and thermo mechanical treatment.
Foil diffusion bonding: Layers of metal foil are sandwiched with long fibres and then pressed through to form a matrix.
Liquid State Methods:
Electroplating/Electroforming: A solution containing Metal Ions loaded with reinforcing particles is co-deposited forming a composite material.
Stir casting: Discontinuous reinforcement is stirred into molten metal, which is allowed to solidify.
Squeeze casting: Molten metal is sprayed onto a continuous fibre substrate.
Reactive processing: A chemical reaction occurs, with one of the reactions forming the matrix and other the reinforcement.
Stir Casting Methods of Fabrication of MMCs:
Liquid state fabrication of metal matrix composite involves incorporation of dispersed phase into a molten matrix metal, followed by its solidification. In order to provide high level of mechanical properties of the composite, good interfacial bonding (wetting) between the dispersed phase and liquid matrix should be obtained. Wetting improvement may be achieved by coating the dispersed phase particles (fibres). Proper coating not only reduces interfacial energy, but also prevents chemical interaction between the dispersed phase (ceramic particles, short fibres) and Matrix.
The simplest and the most cost effective method of liquid state fabrication is Stir Casting.
3.4 Stir Casting:
Stir Casting is a liquid state method of composite materials fabrication, in which a dispersed phase (ceramic particles, short fibres) is mixed with a molten matrix metal by means of mechanical stirring. The liquid composite material is then cast by conventional casting methods and may also be processed by conventional Metal forming technologies.
Stir Casting is characterized by the following features:
Content of dispersed phase is limited (usually not more than 30 vol.%).
Distribution of dispersed phase throughout the matrix is not perfectly homogeneous :
There are local clouds (clusters) of the dispersed particles(fibers);
There may be gravity segregation of the dispersed phase due to a difference in the densities of the dispersed and matrix phase.
The technology is relatively simple and low cost.
Distribution of dispersed phase may be improved if the matrix is in semi-solid condition.
The method using stirring metal composite materials in semi-solid state is called Rheocasting.
High viscosity of the semi-solid matrix material enables better mixing of the dispersed phase.
Fig No. 3.1. Stir Casting Set Up (Line Diagram)
Fig 3.2 Stir Casting Set Up (Actual)
3.5 Graphite :
Graphite, archaically referred to as Plumbago, is a crystalline allotrope of carbon, a semi metal, a native element mineral, and a form of coal. Graphite is the most stable form of carbon under standard conditions. Therefore, it is used in thermochemistry as the standard state for defining the heat of formation of carbon compounds.
3.5.1 Types and Varieties :
Crystalline small flakes of graphite occurs as isolated, flat, plate-like particles with hexagonal edges if unbroken. When broken the edges can be irregular or angular.
Amorphous graphite : Very fine flake graphite is sometimes called as amorphous.
Lump graphite occurs in fissure veins or fractures and appears as massive platy intergrowths of fibrous or acicular crystalline aggregates, and is probably hydrothermal in origin.
Highly ordered pyrolytic graphite refers to graphite with angular spread between the graphite sheets of less than 1o.
The name “graphite fiber” is sometimes used to refer to carbon fibers or carbon-reinforced polymer.
3.5.2 Properties :
Graphite has a high melting point, similar to that of diamond. In order to melt graphite, you have to break the covalent bonding throughout the whole structure.
Graphite has a soft, slippery feel, and is used in pencils and as a dry lubricant for things like locks.
Graphite has a lower density than diamond. This is because of relatively large amount of space that is wasted between the sheets.
Graphite is insoluble in water and organic solvents-for the same reason that diamond is insoluble (there are no possible attractions which could occur between solvent molecules and carbon atoms which could outweigh the attractions between the covalently bound carbon atoms).
Graphite conducts electricity. The delocalized electrons are free to move throughout the sheets. If a piece of graphite is connected into a circuit, electrons can fall off one end of the sheet and be replaced with new ones at the other end.
3.5.3 Use of Natural Graphite :
Foundry facings and lubricants
3.5.4 Use of Synthetic Graphite :
Powder and scrap
3.6 Why Graphite ?
Lubricating quality : reducing friction during compaction.
High resistant to corrosion resulting into long life of the components.
Increases overall hardness of the aluminium upto certain level.
Increases the tensile and yield strength of the metal.
Superiorises the wear strength of the base metal with which it is reinforced.
3.7 Interfacial Parameters :
The desired properties of MMC’s namely strength, stiffness, fracture, toughness, good creep and fatigue resistance are significantly influenced by the nature of the interface between reinforcement and matrix.
3.8 Criteria which are important in considering the interface that exists in a MMC material :
Adsorption and Wetting
Adsorption and Wetting:
Good wettability is needed to generate a strong interface that will allow transfer and distribution of load from the matrix to the dispersed phase, without premature. Thermodynamically reversible work needed to separate interface into its component parts:
Wa = Ys +YL-YSL………………………………(1)
YS = Surface energy of solid
YL= Surface energy of liquid
YSL= Interfacial energy of solid-liquid phase
Young – Dupre’s equation:
YS= YSL+ YLcosØ(2)
Ø= contact angle
Combining (1) and (2)
Wa= YL (1 + cos Ø)
Thus from a knowledge of Ø and YL, the work of adhesion can be found out.
Fig. No. 3.3. Liquid drop on the solid surface
For Ø =1800, the drop is spherical with only point contact with the solid and no wetting takesplace.
For Ø =00, the wetting is PERFECT.
For Ø ;O;180O, the degree of wetting increases as Ø decreases.
Adsorption –It is a surface reaction which is dependent on concentration, temperature, and diffusivity. The greater the adsorption, the more the solute tends to lower the surface energy.
Inter-diffusion plays only a minor role at low temperatures, but at elevated temperatures approaching the mp of the matrix, inter-diffusion and chemical reaction can result in the formation of brittle inter nmetallic which are detrimental to the mechanical properties of MMCs.
For strong chemical bonding between the reinforcement and matrix a controlled amount of chemical reaction at the interface is always desirable. However, too thick an interfacial zones adversely the mechanical properties of the composites and leads to premature failure.
Improvements in interfacial bonding in MMC are generally achieved by two means:
Surface treatment of the reinforcement- The reinforcement surfaces are coated with suitable materials to improve wettability and adhesion and also to prevent any adverse chemical reactions at elevated temperature.
Eg : 1. Coatings of SiC on boron fibre for Al matrices.
2 B4C coating on boron fibres for titanium matrices.
Matrix Modification- It is done by modifying the matrix alloy composition.
Eg : Alloying the Al matrix with lithium promotes the wetting of polycrystalline Al2O3 fibres. The Lithium is believed to react with alumina to form a lithium aluminate which is more readily wetted by aluminium.
“Alloying can minimize unwanted interfacial reactions”.
Mechanical Adhesion :
Mechanical bonding plays a major role in load transfer by shear. Two separate factors affect mechanical adhesion namely,
(1). Surface roughness, which controls the amount of mechanical interlocking that can occur.
(2).The presence of residual stresses in the matrix as a result of fabricate.
Example : Carbon and aluminium fibres posses small surface irregularities that affect the apparent fibre matrix bond.
3.9 Points to Remember :
For strong chemical bonding between the reinforcement and matrix a controlled amount of chemical reaction at the interface is always desirable. However, too thick an interfacial zones adversely the mechanical properties of the composites and leads to premature failure.
Interfacial reactions are of concern as they can adversely affect the mechanical performance of an MMC. So, it is clear that, as a general rule, extensive interfacial reactions should be avoided if optimum mechanical performance is to be achieved with MMC’s.
3.10 Mechanical Testing:
There are two type of the mechanical testing which was carried out in this work:
Tensile Testing on programmable UTM.
Hardness Testing on Rockwell Hardness Testing Machine and Vickers Hardness testing machine.
Mechanical testing plays an important role in evaluating fundamental properties of engineering materials as well as in developing new materials and in controlling the quality of materials for use in design and construction. If a material is to be used as part of engineering structure that will be subjected a load, it is important to know that the material is strong enough and rigid enough to withstand the loads that it will experience in service. As a result engineers have developed a number of experimental techniques for mechanical testing of engineering materials subjected to tension, compression, bending or torsion loading.
16751304718053.10.1 Tensile Testing :
Fig No. 3.4. Schematic Diagram of setup of Tensile Test
Fig No.3.5. Computerized Universal Testing Machine
Tensile properties are used in selecting materials for different applications. Material specifications often include minimum tensile properties to ensure quality so tests must be made to guarantee that materials meet these specifications. Tensile properties are also used in research and development to compare new materials or processes. With plasticity theory, tensile data can be used to predict a material’s behaviour under forms of loading other than uni axial tension.
Often the primary concern is strength. The level of stress that causes appreciable plastic deformation is called its yield stress. The maximum tensile stress that a material carries is called its tensile strength (or ultimate strength or ultimate tensile strength). Both measures are used, with appropriate caution, in engineering design. A material’s ductility may also be of interest. Ductility describes how much the material can deform before it fractures. Rarely, if ever, is the ductility incorporated directly into design. Rather, it is included in specifications to ensure quality and toughness.
Figure shows a typical tensile specimen. It has enlarged ends or shoulders for gripping. The important part of the specimen is the gauge section. The cross sectional area of the gauge section is less than that of the shoulders and grip region, so the deformation will occur here. The gauge section should be long compared to the diameter (typically, four times). The transition between the gauge section and the shoulders should be gradual to prevent the larger ends from constraining deformation in the gauge section.
1397000681990The gripping system should ensure that the slippage and deformation in the grip region are minimized. It should also prevent bending
Fig No. 3.6. Shape of Specimen for Universal testing Machine
Stress-Strain Curve :
1293495157480Fig. No. 3.7. Typical engineering stress strain behavior to fracture point F. The tensile strength TS is indicated at point M. The circular insets represents the geometry of the differed specimen at various points along the curve.
Above Figure shows a typical engineering stress–strain curve for a ductile material. For small strains, the deformation is elastic and reverses if the load is removed. At higher stresses, plastic deformation occurs. This is not recovered when the load is removed. Bending a wire or paper clip with the fingers illustrates the difference. For small strains, the deformation is elastic and reverses if the load is removed. At higher stresses, plastic deformation occurs. This is not recovered when the load is removed. If the wire is bent, a small amount of it will snap back when released.
However, if the bend is more severe, it will only partly recover, leaving a permanent bend. The onset of plastic deformation is usually associated with the first deviation of the stress–strain curve from linearity.*
* for some materials, there may be nonlinear elastic deformation.
As long as the engineering stress–strain curve rises, the deformation will occur uniformly along the gauge length. For a ductile material, the stress will reach a maximum well before fracture. When the maximum is reached, the deformation localizes forming a neck.
The tensile strength (or ultimate strength) is defined as the highest value of the engineering stress. For ductile materials, the tensile strength corresponds to the point at which necking starts. Less ductile materials fracture before they neck. In this case, the fracture stress is the tensile strength. Very brittle materials (e.g., glass) fracture before they yield. Such materials have tensile strengths, but no yield stresses.
Two common parameters are used to describe the ductility of a material.
One is the percent elongation, which is simply defined as,
%El = (Lf ? Lo)/Lo × 100%
Where, Lo is the initial gauge length and Lf is the length of the gauge section at fracture. Measurements may be made on the broken pieces or under load. For most materials, the elastic elongation is so small compared to the plastic elongation that it can be neglected. When this is not so, as with brittle materials or with rubberlike materials, it should be made clear whether or not the percent elongation includes the elastic portion.
The other common measure of ductility is the percent reduction of area at fracture, defined as,
%RA = (Ao ? Af)/Ao × 100%
Where Ao is the initial cross-sectional area and Af is the cross-sectional area of the fracture. If the failure occurs before the necking, the %El can be calculated from the
%RA by assuming constant volume. In this case,
%El = %RA/ (100 ?%RA) × 100%
The %El and %RA are no longer directly related after a neck has formed.
Percent elongation, as a measure of ductility, has the disadvantage that it combines the uniform elongation that occurs before necking and the localized elongation that occurs during necking. The uniform elongation depends on how the material strain hardens rather than on the fracture behaviour. The necking elongation is sensitive to the specimen shape. With a gauge section that is very long compared to the diameter, the contribution of necking to the total elongation is very small. On the other hand, if the gauge section is very short, the necking elongation accounts for most of the elongation. For round bars, this problem has been remedied by standardizing the ratio of the gauge length to diameter at 4: 1. However, there is no simple relation between the percent elongation of such standardized round bars and the percent elongation measured on sheet specimens or wires.
Percent reduction of area, as a measure of ductility, does not depend on the ratio of the gauge length to diameter. However, for very ductile materials, it is difficult to measure the final cross-sectional area, especially with sheet specimens.
3.10.2 Hardness Testing:
Another mechanical property that may be important to consider is hardness, which is a measure of a material’s resistance to localized plastic deformation (e.g., a small dent or a scratch). Early hardness tests were based on natural minerals with a scale constructed solely on the ability of one material to scratch another that was softer.
A qualitative and somewhat arbitrary hardness indexing scheme was devised, termed the Mohs scale, which ranged from 1 on the soft end for talc to 10 for diamond.
Quantitative hardness techniques have been developed over the years in which a small indenter is forced into the surface of a material to be tested, under controlled conditions of load and rate of application. The depth or size of the resulting indentation is measured, which in turn is related to a hardness number; the softer the material, the larger and deeper the indentation, and the lower the hardness index number. Measured hardnesses are only relative (rather than absolute), and care should be exercised when comparing values determined by different techniques.
Hardness tests are performed more frequently than any other mechanical test for several reasons:
They are simple and inexpensive—ordinarily no special specimen need be prepared, and the testing apparatus is relatively inexpensive.
The test is non-destructive—the specimen is neither fractured nor excessively deformed; a small indentation is the only deformation.
Other mechanical properties often may be estimated from hardness data, such as tensile strength.
Rockwell Hardness Tests
The Rockwell tests constitute the most common method used to measure hardness because they are so simple to perform and require no special skills. Several different scales may be utilized from possible combinations of various indenters and different loads, which permit the testing of virtually all metal alloys (as well as some polymers). Indenters include spherical and hardened steel balls having diameters of 1.588, 3.175, 6.350, and 12.70 mm, and a conical diamond (Brale) indenter, which is used for the hardest materials.
With this system, a hardness number is determined by the difference in depth of penetration resulting from the application of an initial minor load followed by a larger major load; utilization of a minor load enhances test accuracy. On the basis of the magnitude of both major and minor loads, there are two types of tests: Rockwell and superficial Rockwell. For Rockwell, the minor load is 10 kg, whereas major loads are 60, 100, and 150 kg. For superficial tests, 3 kg is the minor load; 15, 30, and 45 kg are the possible major load values. These scales are identified by a 15, 30, or 45 (according to load), followed by N, T, W, X, or Y, depending on indenter. Superficial tests are frequently performed on thin specimens. Table 6.6b presents several superficial scales. When specifying Rockwell and superficial harnesses, both hardness number and scale symbol must be indicated. The scale is designated by the symbol HR, followed by the appropriate scale identification. For example, 80 HRB represents a Rockwell hardness of 80 on the B scale, and 60 HR30W indicates a superficial hardness of 60 on the 30W scale.
Brinell Hardness Tests:
In Brinell tests, as in Rockwell measurements, a hard, spherical indenter is forced into the surface of the metal to be tested. The diameter of the hardened steel (or tungsten carbide) indenter is 10.00 mm (0.394 in.). Standard loads range between 500 and 3000 kg in 500-kg increments; during a test, the load is maintained constant for a specified time (between 10 and 30 s). Harder materials require greater applied loads. The Brinell hardness number, HB, is a function of both the magnitude of the load and the diameter of the resulting indentation. This diameter is measured with a special low-power microscope, utilizing a scale that is etched on the eyepiece. The measured diameter is then converted to the appropriate HB number using a chart; only one scale is employed with this technique.
Semiautomatic techniques for measuring Brinell hardness are available. These employ optical scanning systems consisting of a digital camera mounted on a flexible probe, which allows positioning of the camera over the indentation. Data from the camera are transferred to a computer that analyzes the indentation, determines its size, and then calculates the Brinell hardness number. For this technique, surface finish requirements are normally more stringent than for manual measurements.
Maximum specimen thickness as well as indentation position (relative to specimen edges) and minimum indentation spacing requirements are the same as for Rockwell tests. In addition, a well-defined indentation is required; this necessitates a smooth flat surface in which the indentation is made.
Vicker’s Hardness Test :
The Vickers hardness test method, also referred to as microhardness test method, is mostly used for small parts, thin sections or case depth work.
The Vickers method is based on optical measurement system. The microhardness test procedure, ASME E-384, specifies a range of light loads using a diamond indenter to make an indentation which is measured and converted to a hardness value. It is very useful for testing on a wide type of materials, but test samples must be highly polished to enable measuring the size of the impressions. A square based pyramid shaped diamond is used for testing in the Vickers scale. Typically loads are very light, ranging from 10gm to 1Kgf, although macro Vickers can bear loads upto 30kgf or more.
The Microhardness methods are used to test on metals, ceramics, composites-almost any type of material.
Since the test indentation is very small in a Vickers test, it is useful for a variety of applications: testing very thin materials like foils or measuring the surface of a part,small parts or small areas, measuring individual microstructures, or measuring the depth of case hardening by sectioning a part and making a series of indentation to describe a profile of the change in the hardness.
Sectioning is usually necessary with a microhardness test in order to provide a small enough specimen that can fit into tester. Additionally, the sample preparation will need to make the specimen’s surface smooth to permit a regular indentation shape and good measurement, and to ensure the sample can’t be held perpendicular to the indenter.
Often the prepared samples are mounted in a plastic medium, to facilitate the preparation and testing. The indentations should be as large as possible to maximize the measurement resolution. (Error is magnified as indentation size decreases) the test procedure is subject to problems of operator influence on the test results.
Fig. No. 3.8 Vickers Hardness test
Fig. No. 3.9. Shape of Indenter for different hardness tests.
Equipment Specifications :
3.11.1 Wooden Pattern :
Wood Material : Kale
Dimensions : 23x23x185 mm2
Moulding Box and Sand :
Dimension of Cope : 210x185x60 mm2
Dimension of Drag : 210x185x65 mm2
Diameter of Sprue : 25 mm
Diameter of Riser : 27 mm
Purpose used for : Stirring
Type of furnace : Muffle Furnace
Capacity of furnace : 950oC
Temp Increasing Rate : Fixed
Purpose used for : Stirring
Type of furnace : Muffle Furnace
Capacity of furnace : 1250oC
Temp Increasing rate : Controllable
Aluminium Grade : 6061
Reinforced material : Graphite Powder
Project Snaps :
Fig. No. 3.10 : Mould Pattern (Front View)
Fig. No. 3.11: Mould Pattern (Side View)
Fig. No. 3.12 : Mould Preparation
Fig. No. 3.13 : Melting Process in Furnace
Fig. No. 3.14 : Pouring Molten Metal to Mould
Fig. No. 3.15 : Final Product : UTM Specimen-For tensile and yield strength testing
Fig. No. 3.16 : Vicker’s hardness test specimen
Fig. No. 3.17 : Brinells Hardness test specimen
4 . RESULT AND DISCUSSIONS
4.1 Mechanical Testing Report (Al 6061)
Fig. No. 4.1 : Mechanical Test Report (Al 6061)
4.2 Mechanical Test Report ( Al 6061+2% Graphite by weight fraction)
Fig. No. 4.2 : Mechanical Test Report (Al 6061+2% graphite by weight fraction)
4.3 Mechanical Test Report (Al 6061+4% graphite by weight fraction)
Fig. No. 4.3 : Mechanical Test Report (Al 6061+4% graphite by weight fraction)
4.4 Mechanical Test Report ( Al 6061+6% graphite by weight fraction)
Fig. No. 4.4 Mechanical Test Report (Al 6061+6% graphite by weight fraction)
4.5 Brinells Hardness Test (performed in college mechanical workshop)
D=5mm, P=100kgf, Hardened Steel ball Indenter (Table No. 4.1)
SPECIMEN BRINELLS HARDNESS TEST
Al 6061 24 BHN
( d= 2.24mm)
Al 6061 + 2%Graphite (by weight) 27 BHN
Al 6061 + 4%Graphite (by weight) 33 BHN
Al 6061 + 6%Graphite (by weight) 21 BHN
4.6 Vickers Hardness Test (performed in college mechanical workshop)
P=30kgf, Square base pyramidal diamond indenter (Table No. 4.2)
SPECIMEN VICKERS HARDNESS TEST
Al 6061 49VHN
Al 6061+2%graphite (by weight) 53 VHN
Al 6061+4%graphite (by weight) 61 VHN
Al 6061+6%graphite (by weight) 43 VHN
5.1 Tensile Test :
By observing the tensile test report it can be seen that the Ultimate tensile strength along with yield strength and percentage elongation increases upto a level on reinforcing graphite powder in Aluminium alloy 6061.
Futhermore, the Ultimate tensile strength increases on increasing the graphite reinforcement in the Aluminium alloy, But would start to decrease after a certain level.
Here, on adding graphite by the variation of 2% by weight to the aluminium alloy, it can be seen that the tensile strength increases upto the 4% graphite reinforcement with base metal but showed a fall/decrease in the same tensile strength when the reinforcement was made to 6% by weight fraction instead of 4%.
Therefore, it can be observed and finally concluded that on adding or reinforcing 4%graphite by weight to Al 6061 alloy would result in an impressive increase in the Ultimate Tensile Strength.
Scale : X-axis : Matrix Compositions
Scale : Y-axis : Ultimate tensile strength (MPa)
Fig. No. 5.1 : Graph showing variation of Ultimate Tensile strength on different specimens of Al 6061 and Graphite compositions.
5.2 Hardness Test :
As observed from the mechanical test report and practical experimentation, the variation among hardness of specimens with different compositions is having the same behavior as of Ultimate tensile strength for these compositions.
That is, the hardness of base metal Al 6061 increases upto an optimum level on addition of graphite reinforcement in particular weight fractions. But again, after a particular composition, there has been seen a decline or fall in the hardness of the material.
Such as, the hardness of the metal increases upto 4% of graphite reinforcement in the base metal Al 6061, but it is seen and observed that at 6% graphite weight there is a decrement in hardness of the metal.
Thus, it has been concluded that the hardness of Al 6061 can be increased upto 4%graphite addition by weight and is reported to be maximum at this composition. Beyond this, the hardness decreases of the metal.
Scale : X-axis : Matrix composites
Scale : Y-axis : Vickers hardness number
Fig. No. 5.2 : Graph showing variation of Hardness (Vickers) on different specimens of Al 6061 and graphite composites.
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