Subsurface Deformation of Worn Al-Cu and Al-Mg Alloys

Abstract

This paper investigates the subsurface deformation of two types of aluminium alloys with differing nature; A2124 (precipitation-hardened) and A5056 (work-hardened), sliding against an M2 tool steel slider. With block-on-ring configuration, the wear test was carried out at different loads ranging from 23 - 140N, in a dry sliding condition. Detailed secondary electron microscopy (SEM) performed on the longitudinal cross sections of the worn alloys indicates that the subsurface deformed layer beneath the worn surfaces is composed of a number of distinct layers like the mechanically mixed layer (MML), the shear deformed and bulk layers with increased hardness as the surface was approached. Deformation below the MML followed the expected behaviour of an exponential decay of strain with depth. In contrast to other studies in the literature, a linear relationship between depth of deformation and specific wear rate was not found for both alloys. This was believed to a result of the MML, which occupied a great proportion of the total depth of deformation. The relationship between the characteristics of the MMLs especially on the work hardening as a function of alloy type is also discussed.