A study of indentation in an AlCuMg alloy

Vickers indentations have been made in the structurally important alloy Al2.5wt.%Cu1.2wt.%Mg and studied using Nomarski contrast, laser scanning microscopy (LSM) and transmission electron microscopy (TEM). Indentations were made after solution heat treatment and room-temperature ageing and it is shown that the pattern of material pile-up depends on the surface orientation but is largely independent of the orientation of the indenter. The same orientation independence was also found for the slip-line pattern near the indentation. It is shown that the stresses calculated on the model due to Swain and Hagan [1] provide a good prediction of the slip observed near indentations in grains of several different orientations. Indentations were also studied after high-temperature ageing. A comparison of the two states of ageing shows that the deformation is more localized in the high-temperature aged state, with much finer slip, but that the patterns of pile-up in the two cases are only slightly modified.