Study On Compound Deformation Technology And Microstructure Property Of AZ31Magnesium Alloy

Magnesium alloy has many advantages, such as high specific strength, and highspecific stiffness, and good electromagnetic shielding effectiveness, and excellentmachining performance, and easy to recycle. Because of its hexagonal crystal structure,magnesium alloy has no enough independent slip systems. The plastic deformation ofmagnesium alloy is mainly based on twinning at low temperature. Although theplasticity of magnesium alloy sheet is improved at high temperature, but it is easilyoxidized. One of the main research subjects is searching new technology to improve theformability of magnesium alloy sheet at room temperature. In this paper, the isothermalcombined deformation technology (ICDT) was used to improve the plastic property ofAZ31magnesium alloy sheet. Following research contents were completed, and someconclusions were obtained.(1) Considered initial grain size, the grain growth model of AZ31magnesiumalloy sheet had been determined, and the activation energy of grain growth had beenobtained.(2) Based on computer simulation methods, the reasonable mold designparameters of ICDT are determined, and the metal flow pattern of AZ31magnesiumalloy sheet is studied by the combined deformation process. Tools of the combineddeformation technology had been designed and manufactured, which had function ofheating. The combined deformation process had been determined, thermalinsulation—rolling—intermediate passes annealing—flattening.(3) Based on theoretical and experimental, the reasonable parameters had beenobtained. The deformation temperature was250℃, and the ratio of teeth—width was1:2, and the ratio of reduction was43%. Deformed by isothermal combined deformationtechnology, the average grain size of AZ31magnesium alloy sheet reached7μm. (4) AZ31magnesium alloy sheet produced by ICDT had been annealed. Themicrostructure was uniform and grain was thinness. The average grain size reached5.17μm, and the hardness was78.54Hv. And the yield strength improved from theoriginal125MPa to159MPa. And the tensile strength increased from the original210MPa to215MPa, and the elongation ratio increased from original7.67%to13.56%.(5) According to the manufacture requirement, a continuous heating device forroller had been designed. It can be used to heat the roller continuously and uniformlyand always online in the process of rolling. And it is easy to control the temperature ofthe roller.