Microstructure Evolution of AZ31 Magnesium Alloy Powders Prepared by Mechanical Milling in Hydrogen Atmosphere

AZ31 magnesium alloy powders were prepared by mechanical milling in a hydrogen atmosphere.Nanocrystalline MgH2 was created by the reaction of magnesium alloy powders and hydrogen attributed to the mechanical force.The microstructure evolution of the alloy during mechanical milling was characterized by means of X-ray diffraction(XRD),scanning electron microscopy(SEM) and transmission electron microscopy(TEM),respectively.The results showed that,during milling,the powders were at first rolled into flakes,and then,with the further increased of the milling time,the powders refined gradually.After milling for 80h,the nanocrystalline MgH2 powders,with grain size of about 10nm and particle size of 1-3μm in average respectively,were obtained.