Mechanical Characterization of Stir Cast Al-7075/B4C/Graphite Reinforced Hybrid Metal Matrix Composites

Abstract

Abstract The modern technology requires the materials with light weight, high strength, high stiffness and superior mechanical properties. The mechanical properties of metal matrix composites (MMCs) are critical to their potential application as structural materials. A systematic examination is required to study the effect of particulate weight fraction on the mechanical properties. Aluminium based metal matrix composites find varied applications in aerospace, defence, automobile, sports equipment and electronics due to their favourable properties. Al 7075 is a light weight castable alloy with moderate hardness and strength and finds applications in automotive and aerospace. The addition of refractory reinforcement generally improves the hardness, tensile strength and high temperature properties of the material. The present investigation focuses on characterization of Stir cast Al-7075/B4C/Graphite reinforced Hybrid Metal Matrix Composites. Adding B4C with varying reinforcement of three cases, in first case 2% constant with varying graphite 1%, 3%, and 5%, in second case 4%, and in third case 6% constant with varying same graphite percentage, the aluminum matrix hybrid composites have been fabricated by stir-casting method at 650 °C. Castings for tensile testing were prepared in circular metal mold of diameter 20 mm and length 120 mm. The specimens of 55×10×10 mm with 2 mm notch for impact test, 20×10×10 mm for microscopy analysis and hardness test are cut from a cast ingot of 100×50×10 mm using CNC EDM wire cutting. Specimens are prepared as per the ASTM standards and Microstructure investigation, ultimate tensile strength, impact strength and hardness measurements have been correlated with the percentage of B4C and Graphite particles. The effects of B4C and Graphite particle content on the mechanical properties were investigated. The grain size by using the mean intercept length method, Standard deviation and 95% confidence intervals were determined at different weight fractions.