Creep behavior of AZ31 magnesium alloy in low temperature range between 423 K and 473 K

The deformation behavior of coarse-grained AZ31 magnesium alloy was examined in creep at low temperatures below 0.5 Tm and low strain rates below 5 · 10–4 s–1. The creep test was conducted in the temperature range between 423 and 473 K (0.46–0.51 Tm) under various constant stresses covering the strain rate range 5 · 10–8 s–1–5 · 10–4 s–1. All of the creep curves exhibited two types depending on stress level. At low stress (r/ G < 4 · 103), the creep curve was typical of class I behavior. However, at high stresses (r/G > 4 · 103), the creep curve was typical of class II. At the low stress level, deformation could be well described by solute drag creep whereas at the high stress level, deformation could be well described by dislocation climb creep associated with pipe diffusion or lattice diffusion. The transition of deformation mechanism from solute drag creep to dislocation climb creep, on the other hand, could be explained in terms of solute-atmosphere-breakaway concept.