Effects of 14H LPSO phase on the dynamic recrystallization and work hardening behaviors of an extruded Mg–Zn–Y–Mn alloy

The Mg₉₄Zn_2.5Y_2.5Mn₁ (at%) alloys were treated with different technology of heat treatment processing, namely water cooling and furnace cooling, to obtain the specimens without and with 14H LPSO phase prior to extrusion. The resultant microstructure and mechanical properties of the extruded Mg₉₄Zn_2.5Y_2.5Mn₁ alloys were investigated. The extruded alloy with 14H LPSO phase exhibited finer grains, lower dynamically recrystallized volume fraction, and additional 14H LPSO phase as well as stronger basal texture as compared to that without 14H LPSO phase. Consequently, the extruded alloy with 14H LPSO phase exhibited higher strength but lower elongation as compared to that without 14H LPSO phase. The detailed reasons for these phenomena were provided and analysed in this paper. In particular, the effects of 14H LPSO phase on the dynamic recrystallization and work hardening behaviors were discussed, The result showed that the presence of 14H LPSO prior to extrusion can hinder the nucleation and growth of DRX grains in the extruded Mg₉₄Zn_2.5Y_2.5Mn₁ alloys. Moreover, the large quantities of 14H LPSO phase not only lowed dynamic recovery rate but also promoted the decrease of θ value at stage Ⅳ.