Study on Grain Refinement and Texture Evolution of Mg-Gd-Y-Zn-Zr alloy processed by Repetitive Usetting-extrusion at decreasing temperature

Abstract:

A homogenized Mg-13Gd-4Y-2Zn-0.5Zr (wt.%) alloy was subjected to repetitive upsetting-extrusion (RUE) process at decreasing temperature from 480 to 370℃. The microstructure and texture development of the alloy during the RUE process was investigated in current study. The results showed that average grain size decreased with increasing cumulative strain and decreasing temperature. Uniform ultrafine-grain structure with an average grain size of 3.4 μm was achieved after 6 passes, i.e., cumulative strain of 8.4. Results revealed that grain refinement was induced by a complicated combination of discontinuous dynamic recrystallization and continuous dynamic recrystallization. Kink of lamellar long period stacking order (LPSO) phases played an important role in the grain refinement through subdividing the coarse grains by inducing recrystallization evolved in the kink bands. After 1 pass of RUE, a strong basal texture was obtained. With increasing RUE passes, the texture was gradually weakened, which resulted from cooperative effect of DRX and the alternative change of loading directions (axial and radial) during RUE processing.