Spheroidization behavior of W phase and transformation process of LPSO phase during solid-solution treatment in Mg–Zn–Y–Mn–Ti alloy

Abstract

The effect of solid-solution treatment on the microstructure and mechanical properties of Mg93·5Zn2·5Y2·5Mn1Ti0.5 alloys was studied by the optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), nanoindentation tester, and an electronic universal testing machine. The results showed that the fishbone-like W phase can be transformed into the spherical W phase by the solution treatment, and the partial bulk 18R LPSO phase along grain boundaries can be transformed into the intragranular lamellar 14H LPSO phase. The spheroidization of W phase and the formation of intragranular 14H LPSO phase effectively improved the mechanical properties of considered alloys. With the increase of solid-solution time, the yield strength, tensile strength, and elongation of alloys initially increase and then decrease. The biggest improvement in mechanical properties was observed for alloys subjected to solid-solution treatment for 40 h; the yield strength, tensile strength, and the elongation were 165 MPa, 265 MPa, and 11.5%, respectively.

Keywords

• Mg–Zn–Y–Mn–Ti alloy
• Solid-solution treatment
• Spheroidization of W phase
• Transformation of LPSO phase