INTERNATIONAL JOURNAL OF APPLIED ENGINEERING RESEARCH, DINDIGUL Volume 1, No 4, 2011

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1 Mechanical characterization of Aluminium silicon carbide composite Neelima Devi. C 1, Mahesh.V 2, Selvaraj. N 3 1 Assistant Professor, Department of Mechanical Engineering, S.R. Engineering College, Warangal, (Affiliated to JNTUH) A.P, India 2 Associate Professor, Department of Mechanical Engineering, S.R. Engineering College, Warangal, (Affiliated to JNTUH) A.P, India 3 Associate Professor, Department of Mechanical Engineering, NIT, Warangal, A.P, India neelima882@yahoo.com ABSTRACT Conventional materials like Steel, Brass, Aluminium etc will fail without any indication. Cracks initiation, propagation will takes place with in a short span. Now a day to overcome this problem, conventional materials are replaced by Aluminium alloy materials. Aluminium alloy materials found to the best alternative with its unique capacity of designing the materials to give required properties. In this paper tensile strength experiments have been conducted by varying mass fraction of SiC (5%, 10%, 15%, and 20%) with Aluminium. The maximum tensile strength has been obtained at 15% SiC ratio. Mechanical and Corrosion behavior of Aluminium Silicon Carbide alloys are also studied. Keywords: Aluminium, Silicon Carbide (SiC), Casting, Corrosion behavior, Tensile strength. 1. Introduction Aluminium alloy materials or simply composites are combinations of materials. They are made up of combining two or more materials in such a way that the resulting materials have certain design properties on improved properties.the Aluminium alloy composite materials consist of high specific strength, high specific stiffness, more thermal stability, more corrosion and wear resistance, high fatigue life. AlSiC, pronounced alsick is a metal matrix composite consisting of aluminium matrix with silicon carbide particles. It has high thermal conductivity ( W/m K) and it is chiefly used in microelectronics as substrate for power semiconductor devices and high density multi chip modules, where it aids with removal of waste heat. The mechanical properties of aluminium alloys reinforced with ceramic particulates are known to be influenced by the particle size and the volume fraction. Arsenault, 1984 has concluded from the series of experiments that 0.2% proof stress and ultimate tensile strength tend to increase, and toughness and ductility decrease with increasing volume fraction of particulate or decreasing particle size. Hashim et al., 1999 have made this type of processing in commercial use for particulate Albased composites. Casting is a probably one of the most ancient processes of manufacturing metallic components. First melting the Aluminium metal with 5%, 10%, 15%, and 20% on mass fraction basis. Pouring it into a previously made mould or cavity which conforms to the shape of the desired component. Allowing the molten metal to cool and solidify in the mould. Removing the solidified component from the mould, cleaning it. The solidified piece of metal, 793

2 which is taken out the mould, is called as casting. Finishing casted object by using lathe machine for required shape and size. 2. Experimentation For the preparation of the Aluminium silicon carbide alloy by using mass basis ratio of 100:5, 100:10, 100:15, and 100:20 are prepared. Figure 1 illustrates the raw materials and samples of Aluminium Silicon Carbide material. Figure 1: Raw materials and Samples of Aluminium Silicon Carbide material 2.1 Mechanical Behavior of Aluminium alloy Materials Aluminium silicon carbide alloy composite materials have many mechanical behavior characteristics that are different from those of conventional engineering materials. Some characteristics of merely modifications of conventional behavior, which are: Isotropic An isotropic body has material properties that are the same in every direction at a point in the body, i.e. the properties are independent of orientation at a point in the body. Orthotropic An orthotropic body has material properties that are different in three mutually perpendicular directions at a point in the body and further, has three mutually perpendicular planes of material property symmetry. Thus, the properties depend on orientation at a point in the body. Anisotropic An isotropic body has material properties that different in all directions at a point in the body. No planes of material property symmetry exist. Again, the properties depend on orientation at a point in the body. 2.2 Corrosion behavior of Al silicon carbide alloy composites 794

3 The corrosion behavior of 6061 Al alloy SiC composites (in as cast and extruded form) have been studied in sea water and acid media. The effects of temperature of both the media and concentration of the acid medium were also investigated. The corrosion behavior was evaluated using electrochemical technique. The studies revealed that corrosion damage of composites exposed to sea water medium was mainly localized in contrast to uniform corrosion observed for base alloy. Further, composites were found to corrode faster than the base alloy even though the attack was mainly confined to the interface, resulting in crevices or pits. This could be attributed to the presence of thin layer of reaction product present at the interface acting as an effective cathode which when continuous would increase the cathode to anode ratio enabling higher localized corrosion. However, the extent of corrosion damage in extruded composites was less possibly due to absence of defects like gas pores in the composites and homogeneity in the distribution of particles. Increase in temperature invariably increased the attack for all the materials studied. This is explained due to the metal dissolution (anodic process) which is governed by the kinetics at that temperature. 2.3 Failure modes In the case of Aluminium silicon carbide alloy composite materials, internal material failure generally initiates much before any change its macroscopic appearance is observed. It can be mainly observed in many forms such as breaking of the Aluminium silicon carbide alloys, micro cracking of the matrix, cracking of alloy material, etc. The effect of internal damage response is observed only when the frequency of internal damage is high. 3. Tension Test In any design work, it is important to consider practically realizable values of strength of the materials used in design. The tension test is one of the basic tests to determine these practical values. The range of values obtained from the tests forms the basis for the size of the material in the products for the factor of safety. The tension test is conducted on a universal testing machine model TUE 600(C) at room temperature. The stretch undergone by the specimen is measured by an elongation scale with a least count of 1 mm fixed to the loading unit for every increment in the load. The simple stress and strain developed in gauge length portion is calculated using the formulae. Stress (σ) = Load/ Original cross sectional area Strain (e) = Increment in length / original gauge length Figure 2 shows the standard tensile test specimen. Measure the original gauge diameter (d) and gauge length of the specimen by means of a vernier caliper & steel rule respectively. Mark gauge length by two tiny dots using a dot punch. Grip the test specimen vertically and firmly between the upper crosshead jaws of the UTM model TUE 600(C) by operating the hard wheels provided on the above two crossheads. Adjust the machine to read zero on the elongation scale by opening the left control valve and closing the right control valve. Select the load measuring range according to the capacity of the test piece by operating the load selector knob present on the right side of the control panel. Fix the pen in the pen holder of the load elongation recording system. 795

4 Figure 2: Standard Tensile Test Specimen Adjust the load indicating pointer (black needle) and dummy pointer (red pointer) to zero position in the dial of the control panel before conducting the actual test. Now close both the left control valve and right control valve completely. To apply the load on the specimen press the pump on button existing on the control panel and then immediately start opening right control valve gradually. While opening the right control valve, the left control valve should be completely closed the load will not be applied on the specimen. Increase the load on the specimen gradually at equal intervals opening the right valve and then record the corresponding increase in length of the specimen from the elongation scale provided at the load elongation recording system. Continue loading the specimen till the yield point reached. This is indicated by the elongation scale showing high valves of extension for the same amount of increase in load. After yield point is reached, continue to apply the load till fracture of the specimen occurs. Immediately after the specimen breaks, press the pump off switch on the control panel, close the right control valve and then open the left control valve slowly to release the load.broken specimen is removed from the machine. By joining the two broken halves of the specimen final length between the gauge points and gauge diameter at neck of the specimen is measured by using a steel rule and vernier calipers respectively. Yield point, ultimate tensile strength, percentage elongation, percentage reduction in area and modulus of elasticity are calculated. After tensile test, the specimens are shown in below figures: 3,4,5,6. Figure 3: Specimen 5 % SiC with Al Figure 4: Specimen for 10 % SiC with Al Figure 5: Specimen 15 % SiC with Al Figure 6: Specimen 20 % SiC with Al 796

5 Figure 7: Stress Strain curve for 5 % SiC Tensile strength: N/mm² % Elongation: 5.42% Figure 8: Stress Strain curve for 10% SiC Tensile strength: N/mm² % Elongation: 5.92% Figure 9: Stress Strain curve for 15 % SiC Tensile strength: N/mm² % Elongation: 5.57% Figure 10: Stress Strain curve for 20 % SiC Tensile strength: N/mm² % Elongation: 6.87% In Figure 7, Stress strain diagram is plotted for 5% SiC with Al and all the points are indicated. In Figure 8, the stress strain diagram for 10% SiC with Al, in Figure 9 stress strain diagram for 15% SiC with Al and in Figure 10, stress strain diagram for 20% SiC with Al are plotted. Out of all these specimens, the tensile strength is more for 15% SiC with Al specimen (94.21 N/mm²). The % Elongation is more for 20% Sic with Al specimen (6.87%). 4. Conclusions Aluminium Silicon carbide alloy composite materials are widely used for a many number of applications like engineering structures, aerospace and marine application, automotive bumpers, sporting goods and so on. Based on our work we have found that the weight to strength ratio for Aluminium silicon carbide is about three times that of mild steel during tensile test. Aluminium silicon carbide alloy composite material is two times less in weight 797

6 than the aluminium of the same dimensions. The maximum tensile strength has been obtained at 15% SiC ratio. This indicates that the Aluminium silicon carbide composite material is having less weight and more strength; it is very much useful in practical aerospace applications. Acknowledgements The author acknowledges with thanks to Raghavendra Spectro Metallurgical Laboratory Hyderabad, National Institute of Technology Warangal, S.R Engineering College Warangal for their technical help. 5. References 1. Arsenault R.J., 1984, The Strengthening of Aluminum Alloy 6061 by Fiber and Platelet Silicon Carbide, Material Science and Engineering, 64 (2), pp Doel.T.J.A, Lorretto.M.H and Bowen.P. (1993), Mechanical Properties of aluminium based particulate metal matrix composites, Journal of composites, 24, pp Gnjidi, X., Boi, D. and Mitkov, M. (2001), The influence of SiC particles on compressive properties of metal matrix composites, Materials Characterization, l47(2), pp Gu, J., Zhang, X. and Gu, M. (2004), Mechanical properties and damping capacity of (SiC + AL2O3.SiO2) / Mg hybrid metal matrix composite, Journal of Alloys and Compounds, Article in press. 5. Gupta, M. and Qin, S. (1997), Effect of interfacial characteristics on the failure mechanism mode of a SiC reinforced A1 based metal matrix composite, Journal of Materials Processing Technology, 67(1 3), pp HashimJ.,LooneyL.,andHashmiM.S.J.,(1999), Metal Matrix Composites: Production by the Stir Casting Method, Journal of Material Processing and Technology, 92, pp Kaynak, C. and Boylu, S. (2005), Effects of SiC [particulates on the fatigue behavior of an Al alloy matrix composite, Journal of Material & Design, Article in press, corrected proof. 8. Kok, M. (2005), Production and mechanical Properties of Al 2 O 3 particlereinforced2024 aluminium alloy composites, Journal of Materials Processing Technology, Vol. 161, pp Poole, W.J. and Charras, N. (2005), An experimental study on the effect of damage on the stress strain behavior for Al Si model composites, Material Science & Engineering, 406 (1 2), pp

7 10. Quin, S., Chen, C.and Zhang, G. (1999), The effect of particle shape on ductility of SiC reinforced 6061 Al matrix composite, Material Science and Engineering, 272(2), pp Zhou W., and Xu Z.M.,(1997), Casting of SiC Reinforced Metal Matrix Composites, Journal of Material Processing and Technology, 63, pp