Solidification pattern and microstructures of AZ91D magnesium alloy through rheoforming

The optical microscope, SEM and EDS were adopted to analyze the rheoforming solidification morphologies and microstructures of deformed AZ91D magnesium alloy after isothermal treatment in semisolid state. The results show that primary α phase can be formed through attachment growth, when the liquid fraction is small; and primary α phase will grow in dendrites, when the liquid fraction is high. Eutectic solidification is carried out in the ways of both dissociated growth and symbiotic growth, depending on the morphology of primary α phase. Liquid with cutectic concentration solidifies into lamina eutectic. During solidification of the liquid pools inside grains, α phase can be formed through attachment growth. The eutectic solidification was mainly carried out in the dissociated pattern.