Rheo-diecasting of AZ91D magnesium alloy by taper barrel rheomoulding process

A self-developed taper barrel rheomoulding (TBR) machine was introduced, and the rheo-diecasting process was implemented by combining TBR machine with the high pressure die casting (HPDC) machine. Microstructural characteristics of the rheo-diecasting components were investigated at different rotation speeds. Flow characteristics and microstructural evolution of the semi-solid slurry during the rheo-diecasting process were analyzed and the mechanical properties of the rheo-diecasting components were studied. The experimental results show that the process is able to obtain such components in which the primary α-Mg particles are fine, nearly spherical and uniformly distributed in the matrix. When the rotation speed of internal taper barrel is 700 r/min, the primary α-Mg particles get a mean diameter of about 45 μm and a shape factor of about 0.81. The magnesium alloy melt has complex stirring-fixed flow characteristics when flowing in TBR machine. Compared with conventional die-casing process, the rheo-diecasting process can improve the mechanical properties of components; especially, the elongation is improved by 80%.