Microstructure and mechanical properties of Mg-Gd-Y-Zn-Zr alloy sheets processed by combined processes of extrusion, hot rolling and ageing

摘要

The microstructure and mechanical properties of Mg-8.2Gd-3.8Y-l.0Zn-0.4Zr (wt%) alloy sheets produced by combined processes of extrusion, large-strain hot rolling and ageing treatment were investigated. The sheet rolled at 300 ℃ was mainly composed of deformed grains while that rolled at 400 ℃ was fully recrystallized, and the LPSO phase distributed at the grain boundaries in both sheets. The sheet rolled at 300 ℃ and then peak-aged at 200 ℃ exhibits 0.2% proof stress (PS) of 454 MPa, ultimate tensile strength (UTS) of 469 MPa and elongation to failure of 1.3% at ambient temperature, and 0.2% PS of 413 MPa, UTS of 457 MPa and elongation to failure of 6.8% at 200 ℃, respectively. While the sheet rolled at 400 ℃ and peak aged at 200 ℃ had lower 0.2% PS and superior ductility. The improvement of strength is ascribed to the fine β' phase precipitated within the grains, the LPSO phase and dispersed cuboid Mg-Gd-Y containing phase located at the grain boundaries.