Indentation creep of a cast Mg-6Al-1Zn-0.7Si alloy

Creep behavior of an Mg-6Al-1Zn-0.7Si cast alloy was investigated by indentation creep in order to evaluate the correspondence of indentation creep results with those obtained by other creep test methods. All creep tests were carried out in the temperature range 423-523 K and under constant loads of 5 and 20 N. Based on the steady-state power-law creep relationship, the average stress exponents of about 5.8 and 11.3, and activation energies of 82.3 and 127.8 kJ/mol were obtained in the low- and high-stress regimes, respectively. These results are in good agreement with those of the impression and conventional compressive creep tests reported in the literature. It is suggested that the operative creep mechanism is pipe-diffusion-controlled dislocation viscous glide in the low-stress regime, and dislocation climb with some sort of back stress, similar to those noted in dispersion strengthening alloys, in the high-stress regime.