Continuous versus interrupted creep in AZ91D magnesium alloy

A qualitative model of the creep process of AZ91D was proposed in the past by the authors on the basis of continuous creep tests, optical and SEM metallography and TEM study. In view of this model, creep resistance in the case of interrupted creep tests is expected to be inferior compared with conventional creep test under the same load and temperature. The results of interrupted creep tests performed in the recent investigation, described in this paper, support the prediction and can be explained on the basis of the above mentioned creep model. The differences between the results of the continuous and interrupted creep test stems from microstructural instability of the alloy. This fact has been verified by heat treating of the alloy and stabilizing the microstructure. The creep behavior of the heat-treated specimens was found to be comparable to that of the as-cast pressure die casting specimen subjected to continuous creep.