Desorption behaviour and microstructure change of nanostructured hydrided AZ31 Mg alloy powders

In order to optimize the dehydriding process for producing nanocrystalline Mg alloy powders by hydriding-dehydriding treatment, nano-structured as-hydrided Mg-3Al-1Zn (AZ31 Mg) (mass fraction) alloy powders were thermally dehydrided at various temperatures from 275 to 375 °C. The kinetics of hydrogen desorption was examined by hydrogen discharge measurement during dehydriding. The microstructure of the as-hydrided and the subsequently fully dehydrided alloy powders was investigated by X-ray diffraction analysis (XRD) and transmission electron microscopy (TEM), respectively. Both the desorption kinetics and the grain size of the alloy after complete dehydriding were found to be strongly dependent on the processing temperature. The higher the temperature, the faster the desorption, and the more significant the grain growth. When the desorption temperature was raised from 300 to 375 °C, the time to achieve complete dehydriding was shortened from 190 to 20 min, and the average grain size increased correspondingly from 20 to 58 nm.