Creep of Al–0.2Sc–0.04Zr alloys after different cold-rolling and ageing combinations

Abstract

The tensile creep of Al–0.2Sc–0.04Zr (wt%) after pre-ageing+cold-rolling+ageing (A+CR+A) and cold-rolling+ageing (CR+A) was comparatively studied in the temperature range from 225 to 300°C. The results show that both A+CR+A and CR+A apparently improve the creep resistance. Comparing to A+CR+A, a much higher creep resistance can be obtained by CR+A. The creep threshold stress at 300°C for CR+A is 50MPa, which is 117% higher than that (23MPa) for A+CR+A; furthermore, it decreases linearly with increasing temperatures. The creep of Al–0.2Sc–0.04Zr after both treatments can still be attributed to the dislocation creep with the existence of threshold stresses. Nevertheless, the much smaller creep activation energy (0.50–0.67eV) than that of pure Al may be associated with fine grain sizes and/or pipe diffusion inside grains.