Effect of pre-strain on the steady state creep of Al-5 wt% Mg

Abstract

Steady state creep in Al-5 wt% Mg was studied at different stresses from 30 to 90 MPa and at temperatures ranging from 563 K to 613 K. For the pre-annealed samples the applied stress sensitivity parameter “n” was found to be stress independent and amounted to 3.9. While, for samples pre-strained by 20% “n” was equal to 3 at low stresses and 6 at high stresses. The activation energy for steady creep was found to be 143 kJ/mole for the annealed specimens. The controlling mechanism was considered to be the diffusion of Mg in Al matrix. For pre-strained samples, however, the activation energy was stress-dependent and varied from 104 kJ/mole to 84 kJ/mole. The predominant process responsible for creep in the cold worked matrix seemed to be cross-slip of dislocations.