Creep mechanisms in an Mg-4Zn alloy in the as-cast and aged conditions

The impression creep behavior of the as-cast and aged Mg-4 wt% Zn alloy was investigated in the temperature range of 423-523 K under constant punching stresses. The ageing treatment resulted in improved creep resistance of the alloy. The creep behavior of the material was divided into high- and low-stress regimes. The stress exponent values of both the as-cast and the aged conditions were close to each other at each temperature and were in the range of 4-6 and 8-10 in the low and high-stress regimes, respectively. The activation energy values of both regimes were stress dependent. The zero-stress activation energy values in the high- and low-stress regimes were close to the activation energy of lattice and pipe diffusion for both conditions, respectively. However, the activation energy decreased by increasing the applied stress. Stress assisted dislocation climb controlled by lattice and pipe diffusion were the dominant creep mechanisms in the alloy in the high- and low-stress regimes, respectively.