EXPERIMENTAL INVESTIGATION OF MECHANICAL PROPERTIES ON ALUMINIUM METAL MATRIX REINFORCED WITH TUNGSTEN CARBIDE ABSTRACT Aluminium metal matrix composites are mostly preferred for their low density

EXPERIMENTAL INVESTIGATION OF MECHANICAL PROPERTIES ON ALUMINIUM METAL MATRIX REINFORCED WITH TUNGSTEN CARBIDE
ABSTRACT
Aluminium metal matrix composites are mostly preferred for their low density, high strength to weight ratio, hardness, corrosion resistance, fatigue and creep resistance. Various experiments and research is going on the field of Aluminium Matrix Composites (AMC) and Metal Matrix composites (MMC). AMC and MMC have wide range of application in several fields like automotive, marine, aerospace, defence, high elevated temperatures etc. The present work reveals the study of mechanical properties of Al LM6-Tungsten carbide MMCs containing tungsten carbide (WC) particulates. In this experimentation there are four samples are prepared by adding 0% WC, 5% WC, 10% WC, and 15% WC respectively by keeping basic matrix material aluminium alloy LM6 constant. The composite so produced was subjected to a mechanical tests. The improvement in mechanical properties: hardness and tensile strength was achieved for the increase in the addition of wt.% of WC particles in LM6 matrix. Also, the tribological behaviour of the composite was studied using pin-on-disc wear test apparatus. The decrease in mass loss was observed for the composite contains 15 wt. % of WC during the wear test among the various composites tested. Microstructure of the composite shows the uniform distribution of reinforced particulate in the metal matrix.

INTRODUCTION
Metal Matrix Composites (MMCs) can be developed with simple, low cost and technically efficient ways. The research in MMCs has been focused on the development of its mechanical properties and improving the
performance potentials as compared to homogeneous metals and alloys. High specific strength and stiffness, high temperature performance and low coefficient of thermal expansion are the important1. It is understood that the elastic properties of MMCs are strongly influenced by micro structural parameters of the reinforcement such as shape, size, orientation, distribution and volume fraction2. AMCs have proved themselves to be a best choice as engineering materials in recent decades. The introduction of a ceramic reinforcement into a metal matrix produces a composite material that yields an attractive combination of physical and mechanical properties which cannot be obtained with monolithic alloys2. Out of different automobile components, aluminium matrix composites (AMCs) have been found to be a more promising material, in brake drums, cylinder blocks, cylinder liners, connecting rods, pistons, gears, valves, drive shafts, suspension components, etc. Attempts have been made to examine the effect of sliding velocity on the wear behaviour of aluminium alloy and composites3.
Aluminium LM6 is an aluminium-silicon alloy. The aluminium silicon alloys possess exceptional casting characteristics, which enable them to be used to produce intricate castings of thick and thin sections. Fluidity and freedom from hot tearing increase with silicon content and are excellent throughout the range. Their resistance to corrosion is very good, but special care is required in machining. In general, the binary alloys are not heat treated; at elevated temperatures their strength falls rapidly. Although of medium strength their hardness and elastic limit are low but they possess excellent ductility.

In recent days, considerable work has been done on tungsten carbide reinforced metal matrix composites as well as fly ash reinforced metal matrix composites. The tungsten carbide is used as reinforcement in Al6061 matrix composites with different weight percentages, references 124. The fabrication is done by stir casting process. Wear resistance increases with increase in WC content, in reference 56.

S.Arivukkarasan, B.Stalin Assistant professor (2017) this research paper illustrates, use aluminium (LM4) as a base metal matrix and tungsten carbide (WC) as reinforcement material. Composites were prepared at 5, 10 and 15 percentages of WC particulates by stir casting process and tested for various for various mechanical properties like tensile, hardness and impact strength. The improvement in hardness was observed for the composite contains 15 weight percentage of WC when compared with LM4. Tensile strength increased with increasing of WC. The mass loss is decreased by increasing the weight percent of WC.

K. Punith Gowda, J. N. Prakash have studied mechanical properties of Al2024-Tungsten carbide MMCs containing tungsten carbide (WC) particulates. The reinforcing particulates in the Al2024 alloy were varied from 0% to 5% by weight. The vortex method of cast production was employed to fabricate the MMCs, in which the reinforcement was poured into the vortex created by stirring the molten metal by means of a mechanical agitator. The composite so produced was subjected to a series of mechanical tests. The results of this study revealed that as the tungsten carbide particle content was increased, there were significant increases in the ultimate tensile strength, hardness and young’s modulus, compressive strength, accompanied by a reduction in its ductility.

R. N . Rao., S. Das (2010) have studied the effect of Sic content and sliding speed on the wear behavior of aluminium alloy and composites using pin on disc apparatus against EN32 steel counter face. These tests were conducted at varying Sic particles in 10, 15 and 25 wt % and sliding speeds of 0.52, 1.72, 3.35, 4.18 and 5.23m/s for a constant sliding distance of 5000m. The results were studied that as the Sic content increases the wear rate and temperature decreases, but reverse trend can be observed for coefficient of friction.
Srikanth .B. G, Amarnath. G. (2015) used aluminium (Al 6061) as a base matrix material and tungsten carbide and fly ash as reinforcements. Fabrication of metal matrix composites was done by stir casting. Tungsten carbide was added in proportions of 1%, 2%, and 3% and Fly ash was added in proportions of 2%, 4%, and 6% on mass fraction basis to the molten material. It is observed that mechanical properties like hardness, tensile strength increases by increase the tungsten carbide and flyash into base matrix material al 6061. Every time addition of tungsten carbide and flyash into base matrix material its mechanical property is improved.

Srikanth .B.G. Amarnath .G (2015) have investigated properties of Aluminium (6061) as the base matrix metal and Tungsten carbide (WC) particulate, Fly ash as reinforcement. Fabrication of MMCs done by stir casting process. Tungsten carbide was added in proportions of 1%, 2% and 3% and fly ash was added in proportions of 2%,4% and 6%. The tribological property of Al metal matrix composites, reinforced with WC and flyash particles is presented. Sliding tests were performed on a pin on disc apparatus under varying loads. It was found that the reinforced WC and fly ash particles could effectively reduce the wear, especially under higher normal loading conditions.
Harish .T.M., Abhijith .R., (2016) illustrated, use aluminium (2024) as a base metal matrix and tungsten carbide as (WC) as reinforcement material. Specimens are fabricated by in-situ casting method. It is observed that mechanical properties like micro hardness, wear resistance increases by increasing the tungsten carbide into base matrix material AL 2024.

Dattatraya .N., Shriyash .s., and Tushar .s., (2016) have explained about the process parameters in stir casting method for production of particulate composite and concluded that this casting process is cost
effective and conventional route for manufacturing of composite material. Material having isotropic nature can be manufactured successfully. Preheating of mould reduces porosity and enhance mechanical properties. Design of stirrer decides the flow pattern of melt.
MATERIALS USED
ALIMINIUM LM6
Aluminium LM6 is an aluminium-silicon alloy. The aluminium silicon alloys possess exceptional casting characteristics, which enable them to be used to produce intricate castings of thick and thin sections. Fluidity and freedom from hot tearing increase with silicon content and are excellent throughout the range. Their resistance to corrosion is very good, but special care is required in machining. In general, the binary alloys are not heat treated; at elevated temperatures their strength falls rapidly. Although of medium strength their hardness and elastic limit are low but they possess excellent ductility.

CHEMICAL COMPOSITION:
S.NO CHEMICAL NAME %
1. Copper 0.1 max
2. Magnesium 0.10 max
3. Silicon 10.0-13.0
4. Iron 0.6 max
5. Manganese 0.5 max
6. Nickel 0.1 max
7. Zinc 0.1 max
8. Lead 0.1 max
9. Tin 0.05 max
10. Titanium 0.2
11. AluminiumRemainder
TUNGSTEN CARBIDE:
Tungsten carbide (chemical formula: WC) is a chemical compound (specially a carbide) containing equal parts of tungsten and carbon atoms. In its most basic form, tungsten carbide is a fine grey powder, but it can be pressed and formed into shapes for use in industrial machinery, cutting tools, abrasive, armor-piercing rounds, other tools and instruments and jewellery.

PROPERTIES:
Chemical formula : WC
Molar mass : 195.85 g.mol-1
Appearance : Grey – black lustrous solid
Density : 15.6 g/cm3
Melting point : 2785 – 2830 OC
Boiling point : 6000OC
Solubility in water : Insoluble
Solubility : Soluble in HNO3, HF
Magnetic susceptibility : 10-5 cm3
Thermal conductivity : 100 w/mkFABRICATION OF COMPOSITE:
Fabrications of composites were done by stir casting method. Initially Aluminium LM6 alloy ingots are kept in a graphite crucible and melt in electric resistance furnace at 800 degrees. The calculated amount of preheated reinforcement of WC at 300 degrees was added slowly into the melt. The stirring setup is brought near the furnace; stirrer is dipped inside the crucible and stirred at 600 rpm. As the impeller rotates it generates a vortex that draws the reinforcement particle into the melt from the surface. The stirring action was carried out about 10 minutes.

After by removing stirred setup, the mixed melt is poured into the required preheated metallic mould. The molten metal is made to solidify and the prepared casting is removed from the mould. The casted composites were machined under lathe machine made to prepare tensile testing, hardness and wear testing specimens as per ASTM standards.
TESTS CONDUCTED
After the specimens were prepared various tests were conducted on the specimens in order to know the mechanical properties of casted composites. The different tests conducted are
Tensile Test
Hardness Test
Wear Test
TENSILE TEST:
Tensile testing, also known as tension testing is a fundamental materials science and engineering test in which a sample is subjected to a controlled tension until failure. Properties that are directly measured via a tensile test are ultimate tensile strength, breaking strength, maximum elongation and reduction in area. From these measurements the following properties can also be determined: Young’s modulus, Poisson’s ratio, yield strength, and strain hardening characteristics. Uniaxial tensile testing is the most commonly used for obtaining the mechanical characteristics of isotropic materials. Some materials use biaxial tensile testing. The most common testing machine used in tensile testing is the universal testing machine. This type of machine has two crossheads; one is adjusted for the length of the specimen and the other is driven to apply tension to the test specimen.

TEST SPECIMEN:
A tensile specimen is a standardized sample cross-section. It has two shoulders and a gage (section) in between. The shoulders are large so they can be readily gripped, whereas the gauge section has a smaller cross-section so that the deformation and failure can occur in this area.

A standard specimen is prepared in a round or a square section along the gauge length, depending on the standard used. Both ends of the specimens should have sufficient length and a surface condition such that they are ?rmly gripped during testing.

SPECIFICATIONS OF SPECIMEN:
OVERALL LENGTH
122mm
DISTANCE BETWEEN SHOULDERS
62mm
GAGE LENGTH
50mm
DIA OF REDUCED SECTION
10mm
WIDTH OF GRIP SECTION
15mm
GRIP SECTION LENGTH
30mm
HARDNESS:
Hardness is a characteristic of a material, not a fundamental physical property. It is defined as the resistance to indentation, and is determined by measuring the permanent depth of the indentation. More simply put, when using a fixed force and a given indenter, the smaller the indentation, the harder the material. Indentation hardness value is obtained by measuring the depth or the area of the indentation.

33337503365500VICKER’S HARDNESS TEST:
The Vicker’s hardness test method, also referred to as a micro hardness test method, is mostly used for small parts, thin sections, or case depth work. The Vicker’s method is based on an optical measurement system. Vickers hardness machine also functions on the same principle as the Brinell hardness testing machine, but employs a square based pyramid made of diamond as the indenter. The size of the indenter is also very small. The included angle between the opposite faces of the pyramid is 136 o .Varying loads from 1.0 kgf onwards to 120 kgf are employed.

WEAR TEST:
PIN ON DISC APPARATUS:
DESCRIPTION OF EQUIPMENT:
Pin on disc apparatus is designed to apply various loads and various speeds, provision is made to conduct tests under dry and lubricated conditions. This apparatus facilitates study of friction and wear characteristics in sliding contacts, sliding occurs between the stationary pin and a rotating disc. The normal load, rotational speed and wear track diameter are the variables to meet the test conditions. While the tangential frictional force and wear are acquired with electronic sensors and stored on PC.

SPECIFICATIONS OF SPECIMEN:
Parameter
Value
Diameter 10mm
Length 32mm
MICROSTRUCTURE OF CAST COMPOSITES:
The microstructures of the composites were evaluated by metallurgical microscope. The microstructures revealed a relatively uniform distribution of WC particles and good interfacial integrity between matrix and WC particles. The microstructures of Al- WC composites containing 0,5,10 and 15 wt. % tungsten carbide are shown in Figs. 4.1, 4.2 and 4.3 respectively. These photo micro structures show that the tungsten particles are of nearly uniform size and are uniformly dispersed in the aluminium matrix. However, micro structural studies reveal that, WC migrated to the grain boundaries. This migration of alloying elements into the grain boundaries leaving behind the dispersoids in the grains result in a higher concentration of tungsten within the grains, which may be one of the main reasons for the increase in strength and soundness of the composite developed. The following are the micro structure photographs.
ALUMINIUM LM6+ 0% WC

ALUMINIUM LM6+ 5% WC

WC
ALUMINIUM LM6 + 10% WC
-32175452193925
ALUMINIUM LM6+ 15% W
RESULTS AND DISCUSSIONTENSILE TEST RESULTS:
Tensile test is conducted for on the Computerized Tensile testing machine. The corresponding Tensile strength values were recorded for four different compositions. The test is carried on all the specimens and following table shows the results obtained.

S.NO MATERIAL COMPOSTION
TENSILE STRENGTH(N/mm2)
1
ALUMINIUM LM6 + 0% WC 118.54754
2
ALUMINIUM LM6 + 5% WC 135.73017
3
ALUMINIUM LM6 + 10% WC 167.28327
4
ALUMINIUM LM6 + 15% WC 192.37132
5080033274000
From the above tabular form and graphs it is found that the tensile strength is increased with the increasing the weight percentage of WC particles. The maximum tensile strength is obtained at the 15% of WC particles.

The increase in the tensile strength can be attributed to the presence of hard WC particulates that impart strength to the matrix alloy, thereby providing enhanced resistance to tensile stresses. There is a reduction in the interspatial distance between the hard WC particulates, which causes an increase in the dislocation pile-up as the particulate content is increased. This leads to a restriction in the plastic flow due to the random distribution of the particulates in the matrix, thereby providing enhanced tensile strength to the composites
HARDNESS TEST RESULTS:
The hardness test of all samples was conducted using Vickers hardness testing machine with applied load of 10kgf during test. For each and every composition, indentation values are taken. The following table shows the reading obtained.

S.NO MATERIAL COMPOSITION APPLIED LOAD(kgf) HARDNESS NUMBER
1 LM6+0% WC
10 77.81
2 LM6+5% WC
10 84.54
3 LM6+10% WC
10 93.6
4 LM6+15% WC
10 103.5

From the above tabular values and graphs it is found that the Hardness is increased as the percentage of WC particles increased. The maximum Hardness is obtained at the 15% of WC.

WEAR TESTS RESULTS: The wear test for all samples was conducted using PIN ON DISC machine. The test is conducted for all the sets of composites at constant speed of 600rpm and durations of 5 min and at 3 different loads. The following table shows the reading obtained.

LM6+0% WC:
S.NO LOAD(kg) SPEED(RPM) WEAR(µm)
1 2.5 600 138
2 5 600 252
3 7.5 600 312
LM6+5% WC:
S.NO LOAD(kg) SPEED(RPM) WEAR(µm)
1 2.5 600 91
2 5 600 103
3 7.5 600 112
LM6+10% WC:
S.NO LOAD(kg) SPEED(RPM) WEAR(µm)
1 2.5 600 67
2 5 600 86
3 7.5 600 74

LM6+15% WC:
S.NO LOAD(kg) SPEED(RPM) WEAR(µm)
1 2.5 600 11
2 5 600 38
3 7.5 600 56

CONCLUSIONS AND REFERENCES
CONCLUSION:
The fabrication of composites were done by stir casting method by using Aluminium LM6 as base matrix and Tungsten carbide as reinforcement with varying weight percentage of 5%, 10% and 15%.

From the different tests conducted and results obtained it is found that the tensile strength of composites was increased as the weight percentage of WC increased when compared to the base metal. The maximum tensile strength is obtained at the 15% of WC particles.

The hardness of the composites was increased as the weight percentage of WC particles increased when compared to the base metal. The maximum hardness is observed at the 15% of WC particles.

From wear test results, Wear loss of composites increased with increase in normal load and wear loss decreased with increase in reinforced material in all normal loads. It is observed that wear resistance is less at unreinforced alloy and higher at reinforcement of WC-15 %.

Microstructure of the composites shows the uniform distribution of reinforced material at different wt%.

REFERENCES:
S. Arivukkarasan, V. Dhanalakshmi, B. Stalin & M. Ravichandran (2017):Mechanical and Tribological Behaviour of Tungsten Carbide (WC) Reinforced Aluminium LM4 Matrix Composites, Particulate Science and Technology, 2017.

K. Punith Gowda1, J. N. Prakash1,2, Shivashankare Gowda3, B. Satish Babu1 “Effect of Particulate Reinforcement on the Mechanical Properties of Al2024-WC MMCs”. Journal of Minerals and Materials Characterization and Engineering, 2015, 3, 469-476.

R.N.Rao, S.Das et al.” Effect of Sic content and sliding speed on the wear behaviour of Aluminium matrix composites”. International journal of engineering research and technology (IJERT), 2010.

Srikanth.B.G., Amarnath.G et al.” Characterisation of aluminium reinforced with tungsten carbide particulate and flyash metal matrix composites”. International journal of engineering research and technology (IJERT), 2015
Srikanth.B.G., Amarnath.G et al.”Microstructure and trobological Behaviour of Aluminium reinforced with Tungsten carbide Particulate and flyash metal matrix composites”. International journal of engineering research and technology (IJERT), 2017
Harish.T.M., Abhijith.R et al. “Fabrication and analysis of aluminium (al 2024) and tungsten carbide (WC) metal matrix composite by in-situ method”. International journal of engineering research and technology (IJERT), 2016
Dattatraya.N, Shriyash.S, Tushar.S “Study of process parameters in stir casting method for production of particulate composite plate”. International journal of engineering research and technology (IJERT), 2016