Mechanical and Tribological Behaviour of Artificially Aged (T6) Al-Zn-Mg-Cu Alloy

Abstract

The present work deals with the effect of aging on the mechanical and tribological properties Al-Zn-Mg-Cu (AA7068) alloy. The mechanical properties such as tensile strength, compressive strength, hardness and sliding wear of the alloy in as cast and heat treated condition were examined in order to achieve the maximum properties. Microstructural examination of the alloy in as cast and heat treated condition was carried out to observe the effect of aging. SEM study was also done to observe the worn surfaces and the mechanism of material removal. It is observed that there is a substantial improvement in the mechanical and tribological properties of the alloy due to heat treatment as compared to the as cast alloy. The microstructural study of the cast alloy shows primary dendrites of aluminium and intermetallic phases around the inter-dendrites regions. Due to the heat treatment, the identity of the dendritic structure is lost, because of uniform distribution of precipitates, wherein intermetallic phases were seen dispersed within the grains and the grain boundaries. Results show that the tensile strength of the heat treated alloy at 210oC aging temperature has increased by 155% as compared to as cast alloy. The compressive strength and hardness of the alloy at 210oC aging temperature shows improvement of 41% and 54% respectively as compared to as cast alloy. Wear loss of the heat treated alloy at 210oC aging temperature has decreased at an applied load of 20, 40, 60 and 80 N in both 1.57m/s and 3.00m/s sliding speed.