Creep behaviors of hot compressed Mg-4Y-2Nd-0.2Zn-0.5Zr alloy with and without aging

Tensile creep behaviors of a hot compressed Mg-4Y-2Nd-0.2Zn-0.5Zr alloy with aging (the AA sample) and without aging (the AS sample) are studied at 473, 493 and 523 K under a wide range of applied stresses. The creep mechanism of the AS sample is dislocation viscous gliding. For the AA sample, the creep mechanism is cross-slip during the early creep stage and dislocation climb and pyramidal slip during the late. Furthermore, the precipitates can be dissolved into the matrix and restarted during the subsequent creep stages. At 473 and 493 K, the AA sample has a better creep resistance than the AS sample, due to the hindering effect of the precipitates on dislocation movement. At 523 K and higher stress levels, the precipitates have limited hindering effect on dislocation movement in the AA sample while the kink bands continue to serve as the strengthening mechanism in the AS sample. The creep resistance of the AA sample becomes lower than that of the AS sample. It is recommended that the AA sample be used in the applications where their service temperature is lower than the pre-aging temperature while the AS sample be used where service temperature is higher than the pre-aging temperature.