Microstructure and high temperature mechanical properties of the Mg-Gd-Y(-Nd)-Zr alloy

Abstract

Mg–Gd system alloys have been widely studied because they are applied in automotive, weaponry and aerospace applications and have a wide range of application scenarios due to the excellent strength and heat resistance properties. This work aims to systematically investigate the microstructure and high temperature mechanical properties of Mg-10Gd-3Y-xNd-0.5Zr alloy, and found that the microstructure of Mg-10Gd-3Y-0.5Zr alloy was mainly composed of α-Mg matrix, Mg5(Gd, Y) phase and Mg24(Y, Gd)5 phase. In which Nd element plays a role in the alloy to promote the precipitation phase precipitation and form the new phase Mg41Nd5, and the appropriate amount of Nd can refine the grain size. Moreover, Mg-10Gd-3Y-xNd-0.5Zr alloy has excellent mechanical properties in room and high temperature, with ultimate tensile strengths above 280 MPa at 200 °C–300 °C, 309 MPa at 250 °C, and especially at 350 °C, the tensile strength is still up to 195 MPa. The main strengthening phases are β'' phase, β′ phase and 18-LPSO (Long-period stacking ordered) phase. The Mg-10Gd-3Y-2Nd-0.5Zr alloy has excellent high temperature creep resistance at (200 °C–300 °C)/(50–90 MPa). When creeping at 200 °C, β′ phase is completely transformed into β'' phase. After creeping at 250 °C, β′ phase is transformed into β phase. After creeping at 300 °C, β phase grows significantly. Meanwhile, when the creep temperature and stress increase, the creep mechanism gradually changes from diffusion and grain boundary sliding mechanism to dislocation slip and dislocation climbing mechanism.

Keywords

• Mg-Gd-Y(-Nd)-Zr
• Microstructure
• Mechanical property
• Creep
• Mechanism