Establishment Of The Constitutive Relationship For Semi-solid AZ61 And Thixo-extrusion Forming

Semi-solid material forming method was taken as one of the-near-net-shape forming having the best future in the 21^th century. It has various advantages compared with the conventional liquid casting method, such as less forming temperature, more longer die life, improved work condition and environment, improved organization and mechanism quality of finished product. As compared with the conventional solid plastic forming, SSM forming has less deformation resistance, energy and cost savings, one-forming for complicated parts.In the paper, the semi-solid AZ61 magnesium alloy that was fabricated by SIMA. Compression tests on semi-solid AZ61 magnesium alloy and the conventional casting alloy were carried out using the Gleeble-1500 dynamic material testing machine at different deformation temperatures and different deformation rates. The relation- ships between stress and strain and the microstructure evolutions for AZ61 magnesium alloy were analyzed in different deformation conditions. The results show that The deformation force was required mainly to overcome particle sliding and particle plastic deformation in thixotropic compression process of high solid phase fraction for semi-solid AZ61 magnesium alloy, in which the sliding between solid particles and plastic deformation of solid particles mechanisms were dominant. The deformation resistance decreased obviously with deformation temperature increasing under the same strain rate condition in thixotropic compression process for semi-solid AZ61 magnesium alloy. The true stress peak value increased with the strain rate increasing under the same deformation temperature. The deformation resistance of semi-solid AZ61 magnesium alloy is obviously smaller than one of conventional casting sample.The constitutive relationship was established for semi- solid AZ61 alloy using multiple nonlinear regression method. A scientific basic provided for both numerical simulation of processing process of semi- solid AZ61 alloy and rational choice and control of processing parameters. The coefficient of regression and statistics testing...