Tensile behaviour of an Al–4 wt.%Cu alloy deformed by equal-channel angular pressing

An Al–4 wt.%Cu alloy in the as-cast, homogenized condition was subjected to equal-channel angular pressing, and tensile tests showed a very good combination of strength and ductility. In order to explain a sharp drop in ductility observed after the first pass only, the equal-channel angular pressing was repeated on the same alloy but in the conventionally extruded condition. Results were similar to those of the as-cast and homogenized material, but the ductility drop was absent. Fractographic observation indicated that the conventional extrusion eliminated solidification pores and voids; hence, the total absence of the ductility drop, whilst equal-channel angular pressing caused the same effect on the as-cast and homogenized group of samples, but only after the second pass. This is an important finding since it shows that equal-channel angular pressing has the capacity of closing solidification defects. Further observation of the stress–strain curves revealed the presence of the Portevin-Le Chatelier effect, whose relationship with dislocation density was tentatively discussed.