Microstructure and mechanical property of Mg–10Gd–2Y–1.5Zn–0.5Zr alloy processed by eight-pass equal-channel angular pressing

Abstract

In this work, a high-strength Mg–10Gd–2Y–1.5Zn–0.5Zr (wt%) alloy was prepared via eight passes of equal-channel angular pressing (ECAP). The microstructures and mechanical properties of as-cast and ECAP alloys were systematically investigated by X-ray diffraction (XRD), optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electronic universal testing machine. The obtained results indicate that the microstructure of as-cast alloy consists of α-Mg dendrite, network Mg3(Gd,Y,Zn) phase and lamellar 14H long-period stacking ordered (LPSO) phase which is precipitated near the boundary of Mg3(Gd,Y,Zn) networks. After eight-pass ECAP, the network Mg3(Gd,Y,Zn) phase is deformed and broken. However, the refined Mg3(Gd,Y,Zn) particles are not distributed uniformly in the matrix, but still aggregated at the interdendritic area. Moreover, the content of 14H lamellas increases obviously, and they become bent and kinked during severe deformation. DRX is activated in the region between Mg3(Gd,Y,Zn) particles and 14H clusters. Compression test at room temperature indicates that the ECAP alloy exhibits excellent mechanical property with compressive strength of 518 MPa and fracture strain of 21.6%. The comprehensive high strength and toughness could be ascribed to the refined Mg3(Gd,Y,Zn) particles, DRX grains and kinked 14H LPSO phase.