Microstructure and mechanical properties of Mg-Gd-Y-Zn-Zr alloy by cyclic expansion-extrusion with an asymmetrical extrusion cavity (CEE-AEC)

Abstract

The effect of cyclic expansion-extrusion with an asymmetrical extrusion cavity (CEE-AEC) passes on microstructure and mechanical properties of Mg-13Gd-4Y-2Zn-0.5Zr (wt%) alloy were investigated in this research. The alloy was subjected to 1, 2 and 3 passes at 480 °C, 460 °C and 440 °C, respectively. Optical microscope (OM), scanning electron microscope (SEM) and electron back-scattered diffraction (EBSD) was used to study microstructure evolution with different passes. The fraction of coarse grains decline and fine dynamic recrystallization (DRX) grains increase with the CEE-AEC process pass increase. The average grain size is refined from 20 μm to 13.6 μm after 2 passes CEE-AEC. In addition, the average grain size drops rapidly to 1.8 μm after 3 passes. The as-received alloy and CEE-AEC processed alloys were subjected to the tensile test at room temperature (RT). The superior mechanical properties at RT with tensile yield strength (TYS) of 348 MPa after 1 pass and fracture elongation of 8.1% can be obtained after 3 passes.