Digital Simulation Of Squeeze Casting Of ZA27 Alloy With Large Ratio Of Height To Diameter

The squeeze casting is also named liquid forging, which is a process merging casting and forging and has the advantages of both casting and forging. Its characteristic is the filling and solidification under high pressure, so the grain is relatively fine, the liability to shrinkage is little, the mechanical property can be comparable with forgeable piece; Because of the close contact between casting and die, the casting has the fine facial quality, considerable accuracy and few mechanical processing remnant. The Zn-Al alloy has many advantages, such as good mechanical property, strong antifriction property, processable property, small density, low melting point, affluent raw material, low cost and so on. But the Zn-Al alloy has a broad solidification temperature scope and considerable density difference, so it has the liability to form shrinkage and segregation under the general casting condition, which leads to the reduction of mechanical property, especially the tenacity and plasticity, which have limited the application. The squeezing casting of Zn-Al alloy merges the advantage of casting and forging and has the broad development under the situation of more and more high demand to casting quality. Up to now, all of the researches were focused on the castings witch ratio of height to diameter is less than 3.0 both interior and exterior, in order to enlarge the applicable extent of squeeze casting, it is essential to carry out the research on squeeze casting with large ratio of height to diameter.In this article, the large FEM software, ANSYS, was employed to simulate the temperature field and the pressure field. During the simulation of temperature field, the whole process was divided into two stages, free solidification and solidification under pressure. The heat-enthalpy method was used to deal with the latent heat allowing for the broad crystallization temperature interval of ZA27 alloy. During the process of squeeze casting, the pressure field is mostly affected by the external solidified metal and the friction resistance between the casting and mould. Therefore, the pressure field was simulated by utilizing the elastic-plastic model coupled with the temperature field after the comprehensive consideration about the characteristics of thepressure field simulation. The coupled simulation means that the result of the temperature field was put on the simulation of pressure field as load. Meanwhile, through altering the friction coefficient, ratio of height to diameter, the pressure loss rules of squeeze casting with large ratio of height to diameter were analyzed and discussed, witch have instructive meaning for broadening the applicable extent and practical production. At last, as the example of squeeze casting with large ratio of height to diameter, the temperature field and stress field of high-leg casting were simulated and analyzed.