Microstructure and tensile properties of thixo-diecast AZ91D magnesium alloy

The thixo-diecasting(TDC)process is the combination of semi-solid billet preparation technology and die casting technology.The TDC process not only keeps the characteristics of thixo-forming but also has high efficiency and low cost.In the present work,the microstructures and mechanical properties of an AZ91D magnesium alloy prepared by the thixo-diecasting(TDC)process were characterized in as-cast condition.The TDC alloy produced exhibits a unique microstructure containingα-Mg solid solution andβ-Mg17Al12intermetallic compound,and there are some small droplets and a small gray globule with eutectic structure in the primaryα-Mg grains.The ultimate tensile strength and elongation of the TDC alloy also increase in comparison with other processes,such as thixocasting.Fracture surface observation shows that a crack mainly originates from the brittle fracture of the eutectic phases.The deformation of ductileα-Mg phase provides the TDC alloy with the main strain.