Deformation Behavior, Microstructure Evolution and Hot Workability of an Extruded Mg-2Y-0.5Zn-0.5Ni Alloy

Deformation behavior, microstructure and hot workability of an extruded Mg-2Y-0.5Zn-0.5Ni (MYZN, at.%) alloy were investigated in the temperature range of RT similar to 300 degrees C and strain rate range of 0.01-1 x 10(-4) s(-1). Besides alpha-Mg, Mg24Y5 and Mg2Y, three kinds of LPSO phases appeared in the extruded MYZN alloy, the lamellar 18R-LPSO phase, the massive 18R-LPSO phase and the thin strip 14H-LPSO phase and stacking faults (SFs) distributed in the grain interior. The tensile tests indicated that the tensile strengths of the alloy decreased, while the elongation increased gradually with increasing temperature and decreasing strain rate. At 300 degrees C with a strain rate of 4 x 10(-4) s(-1), the extruded alloy indicated a quasi-superplasticity with an elongation of 130.3%. The extruded alloy exhibited a dislocation slipping at lower temperatures (< 200 degrees C) with different strain rates, while grain boundary sliding assisted dislocation slipping at 300 degrees C. Also, the optimum processing window is 247-300 degrees C/4 x 10(-4)-1 x 10(-3) s(-1).