The influence of minor boron on the precipitation behavior of LPSO phase and dynamic recrystallization in the Mg94Y2.5Zn2.5Mn1 alloys

The influence of minor boron on the microstructure and mechanical properties of solution-treated and as-extruded MX94Y2.5Zn2.5Mn1 alloys has been investigated in this paper. The mechanisms of long period stacking ordered (LPSO) phase transformation during solid-solution treatment and dynamic recrystallization (DRX) in the process of extrusion were analyzed. Experimental results demonstrate that the boron addition effectively promotes the precipitation of 14H LPSO phase and reduces the area fraction and average size of the W phase particles in the solution-treated Mg94Y2.5Zn2.5Mn1 alloy. Furthermore, boron delays the dynamic recrystallization process due to increased 14H LPSO phase during extrusion process. And two kinds of DRX were observed in as-extruded alloys. Finally, the boron addition improves the mechanical properties of both the solution-treated and as-extruded Mg94Y2.5Zn2.5Mn1 alloys. Especially, the as-extruded Mg94Y2.5Zn2.5Mn1 alloy with 0.003 wt% boron addition exhibited optimal mechanical performance with ultimate tensile strength (UTS) and elongation of 389.7 MPa and 24.9%, respectively.