| The process and properties of bar-shaped ZA27 alloy squeeze casting were studied in this paper. The influence of squeeze casting technique on mechanical properties and microstructure of bar-shaped ZA27 alloy was investigated. The effect of heat treatment on mechanical properties and microstructure of squeeze casted bar-shaped ZA27 alloy was also discussed.The results show that the mechanical properties index of bar-shaped ZA27 can attain the level: tensile strength σb≥420MPa, elongation δ5≥ 12%, hardness HBS≥130 under the processing parameters that specific pressure 750MPa, mould temperature 170℃200℃, pouring temperature 630℃, pressure holding time 45s. Squeeze casting can remarkably improve the combination properties of bar-shaped ZA27 alloy, e.g. tensile strength is increased about 18%, hardness about 24%, and elongation about double and the mechanical properties diversity of different parts of the same casting is reduced.Squeeze casting can apparently ameliorate the macrostructure of bar-shaped ZA27 alloy. Under pressure the macrostructure is compacted without serious deficiency such as shrinkage cavity, shrinkage porosity, pore and so on. Squeeze casting can also apparently ameliorate the microstructure of bar-shaped ZA27 alloy. The microstructure changes to flowerlike dendritic from treelike crystal after squeezing. Squeeze casting also changes the shape of intercrystal eutectics and the distribution of e phase. Eutectics are changed to small lamellar shape from large strip shape, and e phase is changed from stick shape or block shape to spot shape, which was dispersed among interdendrities. Under pressure the structure of different parts of the same cast still appears some discrepance. The microstructure of the upper part and lower part is finer than that of the middle part .The microstructure of outboard is finer than that of the inside. The microstructure of center part is fine equiax crystal. The microstructure of outboard is close grain with the feature of deforming structure.Squeeze casting can not only improve the gravity segregation and distribution of the chemical constitution of the cast but also the microsegregation of bar-shaped ZA27 alloy.Squeeze casting can decrease the segregation ratio of Zn, Al, Cu, and increase the Al content of intercrystal eutectic and the Cu, Zn content of a dendritic.Heat treatment can uniform the structure of bar-shaped ZA27, and make it obtain better combination properties after 320°C x8h water quench+180 "C x6h aging.
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