Research On The Thermal Deformation Behaviors Of Squeeze Casting Magnesuim Alloy AZ81

On the basis of the patent (2004100400867,2004.6.23.)of cast-forging compound forming technology, this paper systemically studied hot compression behavior at high temperature of AZ81 magnesium alloy and the evolution rules of microstructures, after making stock by squeeze-casting and homogenization. According to the experiment data of thermal simulation, the constitutive models including deforming temperature, stain rate and deformation quantity, and recrystallization dynamics models were established by numerical analysis. And then using the models above, the compression process at high-temperature was simulated by computer.The main perorations is as follows:1. The microstructure of squeeze-casting samples consist of rough primary crystalsα-Mg matrix and highly mixed eutectic microstructureα-Mg +β-Mg17Al12. The stuffs prepared by squeeze casting, perform better comprehensive mechanical properties than the ones by semi-continuous casting. Tensile strength, yield strength and elongation rate of squeeze-casting samples get great improve.2. AZ81 magnesium alloy squeeze-casting stock are homogenized at 400℃for 8 hours. The discontinuous precipitated phases of alloy basically disappear, and dendritic segregation are completely cleared up. The microstructures of alloy are well-distributed, and the average grain size is 25μm .Tensile strength and elongation rate increase in a certain degree; the yield strength and hardness decrease, which means the plastic forming ability of alloy was made better.3 The evolution of hot forming of AZ81 magnesium squeeze-casting alloy is investigated under hot deformation. The statistic model of stress and strain was established by introducing the Zener-Hollomon parameter and using numerical analysis .4 According to the experiment data of thermal simulation, the effect of deforming parameter such as temperature and strain rate, on microstructure of alloy was analyzed. And the recrystallization dynamics models were established. 5. Besides on the models above, the compression process of AZ81 magnesium squeeze-casting alloy at high-temperature was simulated with DEFORM-3D. And the validity and applicability of above models are inspected and verified. In order to provide basis for predicting the microstructures and performance of forging magnesium alloy and designing preforming stock's structure.