Grain growth kinetics of bulk AZ31 magnesium alloy by hot pressing

Bulk AZ31 magnesium alloy was prepared by hot pressing followed by isothermal and isochronal annealing treatments. A study on the kinetics of grain growth was carried out. X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM) were employed as analyzing tools for the structural evolution and thermal stability at elevated temperatures. The grain sizes were determined by the broadening of X-ray lines and TEM. The results showed that for annealing at temperature range of 300-400 °C, the grain growth kinetics can be well interpreted by the kinetic equation, ^Dn-D0n=kt, where k = k ₀e ^(-Eg/RT). The grain growth exponent n and activation energy E _g were calculated based on the experiment data. The activation energy for grain growth E _g was found to be 110 kJ/mol, which was higher by 18 kJ/mol than that for pure magnesium.