Creep and Mechanical Properties of a Commercial Aluminum Alloy Processed by ECAP

Abstract

A commercial spray-cast aluminum alloy, having a composition of Al-11.5% Zn-2.5% Mg-0.9% Cu-0.2% Zr, was processed by equal-channel angular pressing (ECAP) to give an ultrafine-grained microstructure with a grain size of ~0.3 μm and a fracturing of the rod-shaped MgZn2 precipitates. The mechanical properties of the alloy were investigated using microhardness testing at ambient temperature and tensile testing at a temperature of 673 K. In addition, creep tests were conducted using a double-shear testing facility at temperatures from 473 to 673 K. The results show the microhardness decreases with increasing numbers of passes in ECAP and high strain rate superplasticity is achieved after processing by ECAP at 473 K for 6 or 8 passes. A maximum elongation of >1000% was recorded at a strain rate of 10-2 s-1 when testing at 673 K. The creep tests show the creep rates are faster in the as-pressed material than in the as-received material when testing at the same applied stress and testing temperature.