Grain refinement and exceptional creep resistance achieved in an as-cast Mg–Y alloy with Al addition

Abstract

Grain refinement strengthening is crucial for Mg alloys. However, refined grains can facilitate grain boundary migration during high-temperature creep, usually unfavorably affecting high-temperature creep properties. Al was incorporated into Mg–Y alloy to address this trade-off between fine-grained structures and creep properties, causing the refinement of the Mg–Y alloy (average grain size of 73.2 ± 2.9 μm) while maintaining excellent creep resistance. At 300 °C/50 MPa, the Al-refined alloy exhibited the minimum creep rate of 1.31 × 10−8 s−1, representing a 62 % reduction compared to that of the Mg–Y alloy without Al refinement. During high-temperature creep, the thermally stable Al2Y and long-period stacking ordered (LPSO)/stacking faults (SFs) phases introduced by Al addition effectively pin grain boundaries and impede dislocation movement, which could thus enhance the alloy's creep resistance. Meanwhile, Al addition reduces stacking fault energy (SFE), rendering dislocation climb more challenging and further enhancing the alloy's creep resistance. This study employs Al to refine Mg–Y alloys, achieving grain refinement while enhancing creep resistance, providing a novel method for developing Mg-RE alloys with both refined grains and creep resistance.