Research on microstructure and mechanical properties of hot extruded Mg-Gd-Y-Sm-Zr alloy at room and high temperatures

Abstract

In this study, the age hardening behavior of hot extruded Mg-8Gd-4Y-1Sm-0.5Zr (GWS841) alloy, mechanical properties and microstructural evolution of hot extruded GWS841 alloy during elevated temperature tensile processes were mainly investigated. The results show that the hot extrusion aged GWS841 alloy possess excellent mechanical properties at room and high temperature, which are 397 MPa, 386 MPa, 376 MPa, and 312 MPa at 25 °C, 200 °C, 250 °C, and 300 °C, respectively. After aging for 200 °C × 96 h, the hot extruded GWS841 alloy reaches its maximum hardness and room temperature tensile strength, and strengthening precipitation phase, being nano β′ phase, approximately 12 nm × 20 nm in size, precipitates simultaneously in three prismatic planes, (1‾21‾0)α、 (1‾1‾20)α and (21‾1‾0)α planes, which present precipitation strengthening behavior. During tensile testing at 200 °C, the strengthening precipitate remains β′ phase. During elevated tensile processes at 250 °C and 300 °C, strengthening precipitation phase undergoes significant transformation at grain boundary, β′ phase → β phase, and additionally, nano precipitation zone formed by rare earth atoms aggregation along grain boundary, which strengthen the grain boundary. During elevated tensile deformation at 300 °C, β′ phase completely disappeared and transformed into nano rare earth atom cluster region uniformly distributing inner grain.