Experimental Research Of Microstructure And Properties Of The AZ31 Wrought Magnesium Alloy

This study comes from the project of national natural science fund"New technology and theoretical research of flexible mold hot drawing forming for Magnesium Alloy.(No. of the project: 50775197)".Magnesium and its alloys are the lightest metal structural materials at present. And they have many advantages such as high specific strength and specific rigidity, strong absorption shock resistance, good heat conduction, good electromagnetic shielding, excellent mechanical machining performance, stable part dimension etc. They have been widely used in the fields of aviation, aerospace, automobile, electronic and appliance industry. Many experts and producers have been devoted to the study on the forming technology for Magnesium Alloy home and abroad. Because of magnesium alloy's close-packed hexagonal crystal structure, it has worse deformability at normal temperature. Consequently, it is difficult to realize a large-scale production of magnesium alloy parts through press forming process, which greatly restricts their applications in structural field. Owing to the significant improvement of ductility with temperature increase, it is possible to manufacture magnesium alloy parts through sheet forming at warm temperatures.The purpose of this paper is to examine the uniaxial tensile behavior, microstructure change, fracture behavior and formability of AZ31 magnesium alloy under different deformation conditions, and to determine the optimum process conditions for the best deformation properties of this alloy, thus supplying a reliable basis for the development and application of the new soft die thermal deep drawing technology of magnesium alloy sheets using solid granules pressure-carrying medium. For this, the following work has been conducted:Uniaxial tensile tests were carried out at the temperature range 100℃~ 350℃and the strain rate range 1×10-3s-1~1×10-1s-1 to evaluate the deformation behavior of AZ31 magnesium alloy. The strain-hardening rates, strain rate sensitivitys and plastic strain ratios at various temperatures and strain rates were calculated. The constitutive relation equations of this alloy were regression deduced through experimental data.The microstructure change was observed by optical microscope. The fracture morphologies of deformed specimens were observed by scanning electronic microscope. So the micro deformation mechanismses under various conditions were analyzed.Cylindrical work pieces thermal deep drawing tests using solid granules pressure-carrying medium at temperature range of 100℃~350℃were carried out to investigate the influences of punch temperatures, sheet temperatures and deep drawing speeds on nonisothermal deep drawability of AZ31 magnesium alloy. Thus the proper temperatures of solid granules and sheet, the proper deep drawing speeds for the best deep drawability of the sheet were determined.