Creep behavior and precipitation evolution of Mg-13Gd-2Y-0.5Zr alloy

Abstract

With exceptional aging hardening effect and a heat resistance temperature up to 250 °C, MgGd alloys have great application prospects in heat-resistant components in new energy vehicle power systems, aviation and aircraft systems, atc. In this study, the creep properties of the Mg-13Gd-2Y-0.5Zr (GW132) alloy at 200–270 °C/ 110–150 MPa are investigated, and the constitutive equation of the steady creep rate is constructed, focusing on the evolution of the precipitated phase in the α-Mg matrix at 250 °C/150 MPa. The alloy exhibits good creep resistance at 200–250 °C/ 110–150 MPa and 270 °C/ 110 MPa. During creep at 250 °C/ 150 MPa for 200 h, the evolution sequence of α-Mg matrix precipitates is mainly β’ phase → β’ + β1 phase → β’ + β1 + β + 18R-LPSO phase, β’, β1, β and 18R-LPSO phases can coexist in the same creep state. The β’ phase is maintained at a large volume fraction and forms a string with the β1 phase. The string-like precipitates are connected to each other to form a continuous dense grid module. Moreover, the β’ phase and the 18R-LPSO phase have excellent high-temperature thermal stability and are coherent with the α-Mg matrix, enabling the alloy to have excellent creep resistance in a certain temperature range. The creep mechanism of the GW132 alloy at 250 °C/ 150 MPa is dominated by the diffusion of Gd and Y atoms and the dislocation slip.