Influence of previous ageing treatments on the strength of an Al-4.3 wt.% Mg-1.2 wt.% Cu alloy processed by ECAE

The interaction of equal channel angular extrusion (ECAE) with precipitation hardening during warm ECAE at 180 degrees C in a Al-4.3 wt.% Mg-1.2 wt.% Cu alloy, annealed at various stages of ageing, was studied by room temperature compression tests and transmission electron microscopy. It was observed that peak aged samples lose much of their strength during ECAE due to fragmentation of precipitates. The highest strength after four ECAE passes (route Bc) at 180 degrees C is obtained with samples in the under-aged condition although in this case dissolution of precipitates into the matrix occurs. After four ECAE passes fine equiaxed grains with an average size of approximately 200 nm with some traces of remnant elongated grains were obtained.