Creep Mechanism of AI-Mg Alloys at High Temperatures

Dislocation density, ρ, during steady-state creep of A1–5.54 at.-%Mg alloy was measured as a function of applied stress (oc= 14.7–68.6N/mm²) and of test temperature (T=573–673 K). Effect of the concentration of magnesium (C=0.52–5.54 at.-%) on ρ, was also studied at 573 K. From the present results together with the data on mechanical behaviour reported previously, it is deduced that the steady-state creep rate in these alloys under the condition where m = 1 and n ≃ 3 (m being the effective-stressexponent of dislocation velocity, and n the applied-stress exponent of steady-state creep rate) can be calculated by the solute-atmosphere dragging model using values of p and of the effectivestress which were obtained experimentally as a function of σc, T, and C.