Creep characteristics of an Al2wt.%Cu alloy in the solid solution range

Abstract

The creep characteristics of an Al2wt.%Cu alloy including the stress exponent, the activation energy for creep and the shape of the creep curve were investigated in the temperature range of 783–843 K, where copper is in solid solution. The experimental data of the alloy, when plotted as creep rate against stress on a logarithmic scale, show the presence of two transitions in the stress dependence of creep rate; at constant temperature, the stress exponent n for creep changes from a value of 4.5 at low stresses (low stress region) to a value of about 3 at intermediate stresses (intermediate stress region) and then increases again to a value of 4.5 at high stresses (high stress region). The activation energies for creep at low, intermediate and high stresses are 155 kJ mol −1, 151 kJ mol −1 and 180 kJ mol −1 respectively. While creep curves obtained in the entire stress range of the investigation exhibit a normal primary stage, the extent of the stage is less pronounced at intermediate stresses ( n = 3.2) than at both low and high stresses ( n = 4.5). The above creep characteristics obtained for Al2wt.%Cu are discussed in the light of recent suggestions and predictions regarding deformation mechanisms in solid solution alloys.