Primary and steady state creep deformation in Zamak5 die-casting alloy at 80°C

For most engineering alloys used at high temperature service, secondary creep is preferably studied, as the steady state deformation is more easily used to predict very long term behaviour. This approach is not applicable for zinc alloys since their primary creep contribution to the overall deformation is not negligible. Primary creep was investigated in the present paper on a Zamak5 die-casting alloy; an attempt was made to assess the primary creep contribution, to detect the transition between primary and secondary creep and to evaluate the effect of ageing time on creep. Analyses of the steady-state period were also done to define the creep mechanism in zinc alloys. Total strain during primary creep was demonstrated to be influenced by ageing times. Finally, metallographic observations were carried out to examine the possible effects of creep deformation on the microstructure; a significant change due to primary creep strain was not observed.