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

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 50 MPa, which is 117% higher than that (23 MPa) 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 (0.50-0.67 eV) than that of pure Al may be associated with fine grain sizes and/or pipe diffusion inside grains.