The Study Of Semi-Solid Thixo-Process Of AZ91D Magnesium Alloy

Semi-solid metal process technology with the advantage of high production efficiency,big casting density,few structure separation,little mechanical machining and etc. is applied in some fields. Because of the facility of heating, transportation of semi-solid billets and easy to achieve auto-control , thixoforming of semi-solid has become one of the prime technics method nowadays.Numerical simulation technology not only simulating the fluid field, the temperature field, stress field and the obvious micro-structure changes, but also forecasting the produce position and severe degree of shrinkage porosity, shrinkage cavity and crack etc. has the guiding meaning to die-casting design of semi-solid metal forming process.This paper expounds a few of primate basic theories in the task. It includes forming and fluid of semi-solid metal, plastic forming theory, cast solidification theory, theory of foundry rheology etc.. These provide right academic basis and explanations for fluid, solidification, final forming in semi-solid metal process.Finite element method (FEM) was used to simulate thixoforming process of semi-solid magnesium alloy AZ91D. The behavior of semi solid AZ91D alloy was performed using the rigid-viscoplastic constitutive model. Geometrical models of FEM were established under software UG, and material and friction models of semi-solid material established by software DEFORM-3D^TM.The stress field, fluid field of semi-solid AZ91D Mg alloy, and forming state of moulds in the thixoforming process were obtained by commercial finite element software DEFORM-3D^TM. Simulations results can forecast procreant positions of cracks, forming etc and serious degree, and academic explanations was provided. Finally, rational moulds were designed by adjusting punch velocity, pressure parameters etc.This article testifies the correctness and the reliability of simulation result...