Effects of aging on the creep properties of hot-compressed Mg-2.5 wt%Nd binary alloy

Tensile creep tests were performed at 523 K on a hot compressed Mg-2.5 wt%Nd binary alloy with peak aging (AA sample) and without aging (AS sample) in this work. The dominant creep mechanisms of AS sample were dislocation climb and pyramidal slip while AA sample was mainly dominated by cross-slip. During creep testing, only plate-like beta(1) precipitate was formed in AS sample while both plate-like beta(1) and lenticular beta' phases were formed in AA sample. Moreover, AA sample had larger scale and higher density of precipitates compared to AS sample. Besides, precipitate-free zones (PFZs) were clearly observed along grain boundaries of both AS and AA samples during their secondary creep stages. And the width of PFZs was narrower in AA sample than that in AS sample. The narrower PFZs, the higher density of beta(1) and beta' phases, and the strong interactions between cross-slip and precipitates effectively enhanced the creep properties of AA sample. As a result, AA sample behaved higher creep resistance in comparison to AS sample under all applied stresses at 523 K. Thus, this method of pre-aging and hot compression is believed to have deep potential in improving the service performance of Mg-Nd series at medium to high temperatures.