Correlation between the characteristics of the mechanically mixed layer and wear behaviour of aluminium, Al-7075 alloy and Al-MMCs

The sliding friction and wear behaviour of aluminium (Al), aluminium alloy 7075 (Al-7075) and SiC particulate reinforced aluminium matrix composites (Al-SiC) have been investigated under dry sliding wear conditions. The wear tests were carried out at a sliding speed of 1 m/s and at normal load ranging up to 220 N. The overall objective of the study is to improve our current understanding with regard to the influence of mechanically mixed layers (MML), which form on the surface of the wearing material during the course of the wear test, on the friction and wear behaviour. The aluminium alloy 7075 was used in both solution treated and aged conditions. The aluminium based metal matrix composites studied contained 10 and 40 vol.% of SiC particles as the reinforcing phase. A detailed characterisation of the MML was carried out using SEM, EPMA and microhardness testing in order to understand the influence of test material and load on the composition, hardness and thickness of the MML formed and in turn the influence of the MML on the friction and wear behaviour. On the basis of the above characterisation, it is demonstrated that the observed friction and wear behaviour of Al, Al-7075 alloy and Al-SiC can be best understood in terms of the formation and fracture rate of the MML rather than the bulk properties of the material.