Microstructure and mechanical property of a high-strength Mg-10Gd-6Y-1.5Zn-0.5Zr alloy prepared by multi-pass equal channel angular pressing

In this work, a high-strength Mg-10Gd-6Y-1.5Zn-0.5Zr (wt.%) alloy was fabricated by successive multi-pass equal channel angular pressing (ECAP). The microstructure and mechanical property of as-cast and ECAP alloys were systematically researched by X-ray diffractometer, scanning electron microscopy, transmission electron microscopy and compression test. The results show that the microstructure of as-cast alloy consists of α-Mg grains, Mg24Y5 networks, 18R blocks, fine 14H lamellas, and few Y-rich particles. After 8 passes ECAP, dynamic recrystallization of α-Mg is developed and their average grain size decreases to about 1 µm. The network Mg24Y5 phase at grain boundaries is broken into small particles with average diameter lower than 0.5 µm. Moreover, 18R blocks are kinked and delaminated, or broken into small particles and blended with Mg24Y5 particles. 14H lamellas grow gradually or are dynamically precipitated within certain α-Mg grains. Compression tests indicate that 8p ECAP alloy exhibits excellent mechanical property with compressive strength of 537 MPa and fracture strain of 17.0%. The significant improvement for both strength and ductility of deformed alloy could be ascribed to DRX grains, refined Mg24Y5 particles, 18R kinking and dynamical precipitation of 14H.