Effects of precipitate origin and precipitate-free zone development on the tensile creep behaviors of a hot-rolled Mg-13wt%Gd binary alloy

In heat-resistant Mg-Gd based alloys, the relationship between the collective effects of precipitate origin and precipitate-free zone (PFZ) development on the creep resistance is still unclear. In this work, a hot-rolled Mg13wt%Gd binary alloy was treated by solid solution (SS sample) and peak aging (AA sample). After peak aging, static precipitated beta ' phases were widely generated and PFZs were directly formed along both sides of the grain boundaries in AA sample. Tensile creep tests were performed at 523 K on both SS and AA samples. During creep testing, dynamic precipitated beta ' phases were gradually generated in SS sample while the beta ' phases persisted as large scales in AA sample. The dominant creep mechanisms of SS sample were twinning and cross-slip composed by a a c + a c + a slip effectively enhanced the creep resistance of AA sample. Accordingly, AA sample behaved a higher creep resistance in comparison to SS sample at 523 K. It is hoped that the roles of precipitate origin and PFZ development in the creep properties can enrich the theories and methods in improving the service performance of Mg-Gd series at medium to high temperatures.

Automated summary

In heat-resistant Mg-Gd based alloys, the presence of static precipitated beta ' phases and directly formed PFZs were found to enhance the creep resistance of the alloy. The dominant creep mechanisms, including twinning and cross-slip, were also identified as key factors contributing to the improved creep resistance of the alloy. The study highlights the importance of precipitate origin and PFZ development in understanding and improving the creep properties of Mg-Gd based alloys at medium to high temperatures.