Effect of rotational-die ECAP parameters on microstructure and mechanical properties of Mg97Y2Zn alloys

In this work, the Mg97Y2Zn (at%) alloys have been processed by the rotary-die (RD) ECAP technique under different temperature or pass conditions to tailor the microstructure and mechanical properties. The results reveal that the DRX ratio (VDRX) increases with the increase of ECAP pass or temperature, weakening the texture intensity. The refinement of DRXed grains saturates after 9 passes of ECAP at 350 °C, while the size of DRXed grains (dDRX) monotonically decreases with the reduction of temperature from 400 °C to 300 °C in the case of the same pass number (9P). The combination of fine dDRX, large VDRX, and directionally arranged LPSO phases along the extrusion direction endows the 350 °C–9P alloy with the optimum strength and ductility synergy, exhibiting the tensile yield strength (TYS) of 267 MPa, ultimate tensile strength (UTS) of 318 MPa, and elongation of 10.3%. However, the larger VDRX, weaker texture, less low-angle grain boundaries combine to improve the elongation (14.7%) of the 400 °C–9P alloy at the expense of the TYS (231 MPa) and UTS (303 MPa). This paper provides useful information to optimize the RD-ECAP parameters for the fabrication of high-performance Mg97Y2Zn alloys.