Role of dynamically precipitated long-period stacking ordered (LPSO) plates on the creep behavior of hot-extruded Mg–Zn–Y alloys with multimodal microstructure
Takahiro Mineta, Wataru Bando, Soya Nishimoto, Naoaki Tsunekawa, Daisuke Takahashi, H. Sato, Koji Hagihara, Michiaki Yamasaki
Abstract
α-Mg/long-period stacking ordered (LPSO) duplex alloys with multimodal microstructures exhibit exceptional mechanical properties. In this study, the influence of dynamically precipitated LPSO plate on the creep behavior of hot-extruded Mg-1Zn-2Y and Mg-0.2Zn-0.6Y alloys with a multimodal microstructure was investigated. In the Mg-1Zn-2Y alloy, both transient and steady-state creep were observed across all applied stress conditions. However, under low-stress conditions, the Mg-0.2Zn-0.6Y alloy exhibited unique creep behavior, where the creep rate initially reached a minimum in the early deformation stage and subsequently increased without transitioning into a well-defined steady-state creep. The dynamic formation of the LPSO plate precipitates was observed in both alloys. TEM/EDS analysis revealed that in the Mg-0.2Zn-0.6Y alloy, depletion of solute atoms occurred within the α-Mg matrix phase due to the LPSO plate precipitation. Considering the concentration exponent, even a minor reduction in solute concentration induces a drastic decrease in the creep rate for low-concentration alloys. Therefore, in the Mg-0.2Zn-0.6Y alloy, the progressive increase in creep rate during deformation is attributed to the diminished contribution of solid-solution strengthening caused by plate-like LPSO precipitation. These findings highlight the necessity of optimizing alloy concentration and microstructural morphology to enhance the high-temperature performance of Mg alloys.