The Research On The Forming Process Of Cup-shaped ZA27 Alloy Squeeze Casting With High Ratio Of Height To Thickness

The fundamental problems of cup-shaped ZA27 alloy squeeze casting with high ratio of height to thickness were studied in this paper. Proper parameters were obtained by designing the thrust head squeeze casting die and carrying on the experiment through debugging different parameters. The influence of squeeze casting on mechanical properties and microstructure of ZA27 alloy was also investigated.The proper parameters of squeeze casting for ZA27 alloy with high ratio of height to thickness are: specific pressure 693 MPa, pouring temperature 590℃, pressurization starting time 25s. Under proper parameters, the mechanical properties can attain the level: tensile strength σ_b≥419MPa and hardness HBS≥132.Squeeze casting can apparently improve the macrostructure of ZA27 alloy. Under pressure the macrostructure is compacted without serious defects such as shrinkage cavity, shrinkage porosity, pore and so on. Squeeze casting can also apparently improve the microstructure of ZA27 alloy with high ratio of height to thickness. The microstructure changes to flowerlike dendritic from treelike crystal after squeezing. The microstructures of the upper part and lower part are finer than that of the middle part .Under certain pressure the structure of different parts of the same casting still appears some discrepancies along the height. The upper part shows the best properties. The microstructure of the upper part and lower part is finer than that of the middle part. The microstructure of center part is fine equiax crystal. The microstructure of outboard is close grain with the feature of deforming structure.The primary solidification process of cup-shaped castings with high ratio of height to thickness was studied, and the forming characteristics of the ZA27 alloy cup shaped casting by thrust head squeeze casting were analyzed.