The effect of natural ageing on the evolution of yield strength during artificial ageing for Al-Mg-Si-Cu alloys

Tensile tests have been conducted at 77 and 293 K in order to examine the effect of natural ageing on the subsequent artificial ageing behaviour of the industrial alloy AA6111. The evolution of the yield stress as a function of ageing time at 180 °C was measured for samples with no natural ageing time and a prolonged period of natural ageing (i.e. T4 material). The nature of the obstacles was characterized in terms of the yield stress temperature dependence by measuring the ratio of the yield stress at 293 K to the yield stress at 77 K. From these measurements, it was possible to characterize the variation in the obstacle properties as a function of artificial ageing time.