Microstructure Evolution Of Zn-(2.00～4.00)%Cu Peritectic Alloy

The effects of composition and solidification process on the microstructure of Zn-(2.00～4.00)%Cu alloy were investigated through the analysis of cooling rate and solidified microstructure. The evolution of solidified microstructures was explained using the peritectic metastable phase diagram.Results show that the microstructure is composed of dispersed primaryεphase and peritecticηphase as the matrix. When the cooling rate is slow, theεphase transforms to dendritic morphology and its content increases with the increase of cooling rate. The nuclear supercooling of peritectic phase decreases with the increase of Cu content in the same mould. A regular lamellar structure consisted ofεphase andηphase is obtained using directional solidification. There is someεphase across the lamellar when the Cu content increased. According to the theory of peritectic metastable phase diagram, because of the nonequibrium effect of interface, the equilibrium peritectic phase diagram would transform to metastable eutectic phase diagram during directional solidification, so the lamellar structure formed.The study on the solidified microstructure of Zn-Cu peritectic alloy shows that the formation of the lamellar coupled structure mainly does not depend on the cooling rate in the solidification procedure, but depends on the one dimensional temperature gradient. The lamellar structure would not be abtained increasing the cooling rate, but without the one dimensional temperature gradient.