Mechanical Properties of Aluminium Mmcs

Aluminium MMCs are extensively used in aircraft, aerospace, automotive and different other fields. Aluminium is preferred as a matrix material in MMCs because of its good engineering properties such as low density, better fabric ability etc. The manufacturing techniques of the aluminium metal matrix composites are classified as Liquid state methods, Semisolid methods and Powder metallurgy methods and Ceramic materials generally used to reinforce Al alloys are SiC, Al2O3, SiO2, Zircon, Boron carbide (B4C).

In this present study stir casting technique is used. Stir Casting is a liquid state method of composite materials in which preheated reinforcement material (Al2O3) particulates is mixed with a molten metal by means of a stirrer and after proper mixing the liquid composite material is then casted in moulds as per required shapes. Investigations made by B.Vijaya Ramnath et al [1], Aluminium matrix composites (AMC) are potential materials for various applications due to their good physical and mechanical properties. The addition of reinforcements into the metallic matrix enhances the stiffness, specific strength, wear, creep and fatigue properties compared to the common engineering materials.

Effect of different reinforcement on AMC’s on the mechanical properties like tensile strength, strain, hardness, wear and fatigue is also discussed in detail. Rajender singh et al [2] The Al/SiC metal matrix composite has applications in many industries. In the present study, Aluminium based metal matrix composite are prepared using stir casting method. The weight percentage of silicon carbide changes from 10% to 30%. The main aim is to determine the ultimate tensile strength, hardness, density and the microstructure of SiC particulate reinforced Al matrix composites as a function of volume of SiC. The specimens manufactured were tested on universal testing machine. The results show that the ultimate tensile strength of the metal matrix composite firstly increases with increase in weight percentage of silicon carbide then decreases in tiny amount. The hardness for different specimens is in variation with silicon concentration. It was found that the hardness increases with increasing weight percentage of silicon carbide. The best results have been obtained at 20% weight fraction of SiC particles. Shubhranshu Bansal et al [3], Al359 alloy was reinforced with Silicon Carbide and Silicon Carbide/Graphite particles using stir casting process, thereafter mechanical and wear properties were investigated. It was found that the hardness of the Al359-Silicon Carbide composite is better than Al359-Silicon Carbide-Graphite composite. Results showed that the wear resistance of Al359 alloy improved with the reinforcement of Silicon Carbide/Graphite material for higher loading, sliding velocities and sliding distance conditions. Jamaluddin Hindi et al [4], the addition of refractory reinforcement generally raises the hardness, tensile strength and high temperature properties of the material.

Accordingly 200-300 micron size SiC reinforced aluminium alloy composite is prepared in laboratory condition. In the present work, Al 6063-SiC composite of 2, 4& 6 wt% as reinforcement are manufactured using conventional stir casting technique. Five trials are performed in each test and the average of three nearby readings is taken in hardness, tensile and impact strength tests. Microstructure shows better dispersion of reinforcement in the matrix. It was found that hardness improves with increase in wt% of SiC reinforcement. Madeva Nagaral et al [5], in this experiment, the preparation of 6061Al composites with different weight percentage of Al2O3 particles up to 0-9% were processed by liquid metallurgy route. For each composite, reinforcement particles were preheated to a temperature of 200°C and then dispersed in steps of three into the vortex of molten 6061Al alloy. XRD analysis revealed the presence of Al2O3 and other phases. The tensile strength and hardness of the resultant composites were examined. It was revealed that the 6061Al- Al2O3 composites have a higher tensile strength than 6061 aluminium alloy with reduced ductility. It was found that an increase in the Al2O3 content in 6061Al alloy contributed in improving the hardness of the composites. Chennakesava Reddy et al [6], the use of investment casting process has been studied to prepare 6063/ Al2O3 metal matrix composites. The tensile properties have been checked. The yield strength and fracture strength increase with increase in volume fraction of Al2O3, whereas ductility decreases. The fracture mode is ductile in 10% volume fraction composite and the brittle fracture is observed in 20% and 30% volume fraction composites. T. Mohan et al [7], This work target is on developing an Aluminium metal matrix composite (AMMC) material for turbocharger components made by wrought aluminium alloy with different weight fractions of aluminium oxide in order to make five different forms of composites. By applying stir casting technique, the fabricated composites are tested for their tensile as well as impact properties. The result shows that composite with higher percentage of aluminium oxide has high tensile strength than other composites.

It has been found from literature reviews, that aluminium based metal matrix composites have been successfully fabricated using stir casting method by three step addition of reinforcement combined with preheating of particulates and the increase in volume fraction of Al2O3 which decreases the fracture toughness of the aluminium metal matrix composites (AMMC). Al2O3, SiC reinforced aluminium metal matrix composites by applying stir casting technique exhibits improved physical and mechanical properties, such as, low coefficient of thermal expansion, high ultimate tensile & impact strength, and hardness. Further, with increasing wt% of Al2O3 shows improvement in tensile strength. Stir casting process is cost effective and prominent for manufacturing of composite material. Processing temperature, stirring time influences on the viscosity of liquid metal and particles distribution, also leads to some chemical reaction between matrix and reinforcements. Speed as well as design of the stirrer blade and preheating processes is also the considerable factors to be considered in the production of cast aluminium metal matrix composites, as these have an impact on properties of casting.