Microstructure evolution of components of ZAlSi8Cu3Fe alloy in processing of thixo-diecasting

The microstructures of components of ZAlSi8Cu3Fe alloy in the process of thixo-diecasting were investigated. The effects of processing conditions on the microstructure of the alloy in the thixo-diecasting procedures of original casting billets, remelting billets and casting components were researched, and the morphological evolution of α-particles in the alloy was analyzed quantitatively. The results show that, the microstructure of the original billets poured at 582 °C consists of rosette-like primary α-particles; in the procedure of remelting, when the temperature rises over solidus, arms in the rosette-like α-particles begin to fuse off from dendritic branches and after further heating, α-particles surrounded by liquid phase are refined by the diffusion of atoms and rounded owing to the least interface stress and interface energy principles; and in the procedure of thixo-diecasting, the morphologic characteristics of α-particles and the distribution of phases in the structure change greatly for the high shear rate under the restricted area of the ingate.