Unveiling the collaborative effects of static precipitation and precipitate-free zone on the compressive creep behaviors of Mg-10.5wt%Y binary alloy

Abstract The creep behaviors of dilute Mg Y alloys have been deeply explored whereas very few researches concerned Mg Y series with high Y concentration. The influences of static precipitation and precipitate-free zones (PFZs) on the creep behaviors are still rarely reported. In this work, the compressive creep tests were performed on the as-solution (AS) sample and the as-aged (AA) sample in a hot-rolled Mg-10.5wt%Y alloy at 493 K, 523 K and 553 K under various stresses. It was found that the creep mechanisms for both AS and AA samples appeared to be independent on the creep temperatures. Specifically, the dominant creep mechanisms of AS sample were twinning and dislocation climb. While the creep behaviors of AA sample were ruled by cross-slip and pyramidal  slip. Dynamic precipitates were formed in AS sample during creep, but they could hardly delay the dislocation movement and twinning. On the contrary, the static precipitates could dramatically retard the cross-slip and interact with pyramidal dislocations in AA sample. Besides, no PFZ was found at 493 K, but PFZs were gradually formed with the temperature rising. At 523 K, PFZs were randomly developed in both AS and AA samples. At 553 K, PFZs were uniformly developed in both AS and AA samples. The wider PFZs in AS sample further induced the deterioration to the creep resistance. It is believed that this work will enrich the theoretical basis and expand the applications of heat-resistant Mg Y based alloys.