Work hardening and plastic anisotropy of naturally and artificially aged aluminium alloy AA6063

The plastic anisotropy of an extruded AA6063 alloy after different heat treatments was investigated in a previous study by Khadyko et al. (2017). The material was available in temper T1 (naturally aged to a substantially stable condition) and directly heat treated to the peak aged, overaged and soft annealed conditions without solution heat treatment. Tensile tests in different material directions were performed for these materials and it was found that the plastic anisotropy depended in a complex way on the heat treatment. In the present study, the experimental programme is extended to investigate further the influence of heat treatment on the plastic anisotropy. The AA6063 extruded alloy is first solution heat treated, and then either naturally aged to temper T4 or artificially aged to tempers T6 (peak aged) and T7 (over-aged). Tensile tests in three material directions are performed for these tempers and in the solution heat treated condition (temper W) to reveal the plastic anisotropy. The microstructure evolution of all these materials is then modelled using a nanostructure model (NaMo), which predicts the size distribution of hardening particles, the solute content, the yield strength and the work hardening. The predictions of NaMo are validated using the available data from the tensile tests and TEM observations, and used to analyse the correlation between the stress-strain behaviour and the heat treatment and microstructure of the different materials.