Creep kinetics in compression of sand cast commercial Zn-Al alloys

The compressive creep behaviour of sand cast ZA8, ZA12, and ZA27 alloys was investigated. Primary creep contraction increased with aluminium content and stress and, with the exception of ZA27, decreased with temperature. Secondary creep rates for ZA8 and ZA27 were similar and 33% less than for ZA12. Creep kinetics obeyed an empirical equation ln t = C′- n ln(σ) + Q/RT where t is the time to a selected strain, σ is the nominal stress, T is the absolute temperature, R is the gas constant, and C′, n, and Q are material constants for each alloy. For total deformations up to 1%, the overall creep resistance increased in the order ZA27 > ZA12 > ZA8. In terms of secondary creep rate, the compressive creep resistance of ZA12 was similar to its tensile creep resistance as reported in the literature, but for ZA27 the creep rate in compression was generally slightly higher.