Tribological behavior of heat treated Al 7075 aluminium metal matrix composites

Abstract

Aluminium metal matrix composites (AMMCs) are developed owing to their excellent properties like light weight, high levels of strength, stiffness and wear resistance. In the present work, an attempt is made to study the effect of two hard phase reinforcement particulates namely, silicon carbide (varying weight percentage) and a constant weight percentage of boron carbide on tribological behavior of Al 7075 alloy matrix. The weight percentages of silicon carbide particulate considered here are 5%, 10%, and 15% whereas for boron carbide a constant 3% weight is used throughout the study. Aluminium alloy as base matrix is reinforced with a mixture of two types of particulates along with magnesium (Mg) 1% as binding element. The composite thus formed is termed as aluminium metal matrix composite. These composites are manufactured by the stir-cast liquid metallurgy method. The unreinforced aluminium alloy and composite specimens are carefully machined using lathe machine and prepared for heat treatment process by subjecting to solutionizing treatment at a temperature of 530°C for 1 h followed by quenching in water. Further the specimens are subjected to artificial aging for durations of 4, 6 and 8 h at a temperature of 175°C. The mechanical and tribological properties of composites and the unreinforced alloys before and after heat treatment are examined by Vickers hardness test machine and pin-on-disc test machine respectively. The wear rate and friction co-efficient are evaluated as a function of applied load, sliding velocity, sliding time, and weight fraction for the heat treated particles. The wear surface morphology and wear mechanism of the pins are investigated using scanning electron microscope (SEM) and are correlated with wear test results.