Effect of initial temper on the creep behavior of a Mg–Gd–Nd–Zr alloy

The effect of initial temper on the tensile creep behavior of a cast Mg–Gd–Nd–Zr alloy has been investigated. Specimens in unaged, underaged and peak-aged conditions exhibit a sigmoidal creep stage between the primary and steady-state creep stage, while the overaged specimens have no such creep stage. Transmission electron microscope observations revealed that sigmoidal creep stage was induced by the dynamic precipitation in the microstructure, and the rapid formation of β₁-phase and β-phase plates takes responsibility for the softening of material in this stage. Comparative evaluation of creep properties of the specimens showed that alloy in overaged condition had creep resistance superior to those in other conditions. Stress and temperature dependence of the steady-state creep rate were studied over a temperature range of 250–300 °C and stress range of 50–100 MPa, and a dislocation creep mechanism was proposed for the alloy.