High-Temperature Creep Behavior of Mg-9Gd-2Nd-1Ca-0.5Zr Alloy

The creep behaviors of Mg-9Gd-2Nd-1Ca-0.5Zr alloy under the temperature 200-250 °C and the applied stress 50-90 MPa for 100 h were studied in a typical creep testing machine. The stress exponent n at different stresses and the creep activation energy Q at different temperatures were discussed. The results show that the aging state Mg-9Gd-2Nd-1Ca-0.5Zr alloy has excellent creep resistance at 200 °C/50 MPa, the steady state creep rate is only 2.675 × 10⁻⁹ s⁻¹, and the stress exponent n and creep activation energy Q are 1.1 and 37 kJ/mol, respectively. As the creep temperature and creep stress increase, the creep strain and steady state creep rate increase gradually. The creep mechanism of the alloy is converted from grain boundary slip at 200 °C/50 MPa to dislocation climb at 225 °C/70 MPa. The power law creep fails at 250 °C/90 MPa. The creep mechanism is mainly influenced by the second phase and becomes more complex. The precipitated phases in the grain interiors are the coarse β₁ phase and β phase after creep. The mechanism of creep fracture of the alloy is converted from brittle transgranular fracture at 250 °C/90 MPa to ductile fracture at 250 °C/70 MPa.