Hot Processing Map And Microstructure Analysis Of AZ61Ce Magnesium Alloy Sheet

In this paper,the hot tensile deformation characteristics,dynamic recrystallization critical conditions,microstructure evolution and hot processing of as-rolled,aged and homogenized AZ61Ce magnesium alloy sheets were investigated,respectively.Uniaxial hot tensile experiments were carried out by using the MTS 8510 test machine at 473 K,573 K,673 K and 723 K,respectively,and the strain rates were 0.003 s^-1,0.01 s^-1,0.03s^-1 and 0.1 s^-1,respectively.The experimental conclusions are as follows:?1?The dynamic strain aging?DSA?phenomenon of the as-rolled,aged and homogenized AZ61Ce sheet at low temperature and low strain rate is affected by the Al content in the ?-Mg matrix,and the higher the Al content in the matrix,the easier the DSA effect occurs.The homogenized AZ61Ce sheet is prone to DSA effect under different deformation rates at 473 K,and the stress-strain curve shows obvious serrated flow.The as-rolled AZ61Ce magnesium alloy sheet exhibits an abnormal increase in flow stress due to the interaction between DSA and dislocations and solute atoms under the deformation conditions of 473 K & 0.003 s^-1 and 573 K & 0.003-0.01 s^-1.For the aged sheet,however,the DSA was only found under the deformation condition of 573 K and 0.003 s–1.?2?According to the constitutive equations of these three different state AZ61Ce magnesium alloy sheets,the hardening index?n?of the as-rolled,aged and homogenized sheets is between 3 and 5,indicating that the thermal deformation mechanism of these three different state AZ61Ce magnesium alloy sheets is mainly the solute drag mechanism.In addition,the rate-controlling mechanism related to the Q value of the as-rolled AZ61Ce sheet is dependent on the dependent variable,while the Q values at the different strains of the aged and homogenized AZ61Ce sheet indicate the rate-controlling mechanism of these two different state alloy sheets are the Al atom diffusion mechanism and the intersection slip mechanism,respectively.?3?The hot deformation critical conditions of the dynamic recrystallization?DRX?of the as-rolled,aged and homogenized AZ61Ce sheets were studied,respectively.The critical strain??_c?values of DRX under different deformation conditions of as-rolled and aged sheets are generally lower than the corresponding ?_c values of the homogenized AZ61Ce sheet,mainly due to the large amount of Mg₁₇Al₁₂ particles contained in the as-rolled and aged materials and more grain boundaries promote the nucleation of DRX grains.In addition,the fine Al₄Ce phase in these three different states of AZ61Ce sheet structure promotes the nucleation of DRX grains to a certain extent when the alloy is deformed at a high temperature,but it inhibits the growth of DRX grains.?4?According to the dynamic material model,the hot processing maps of the as-rolled,aged and homogenized AZ61Ce sheets under experimental conditions were established.The workability domain of the as-rolled AZ61Ce sheet is 673-723 K &0.01-0.05 s^-1,and the workability domain of the aged sheet is 473-673 K & 0.005-0.02s^-1 and 673-723 K & 0.003-0.02 s^-1,and the workability domain of the homogenized sheet is 633-723 K & 0.003-0.1 s^-1.In the three different states of the AZ61Ce sheet studied in this paper,the range of thermal processing parameters of the homogenized sheet is the largest,the aging sheet is the second,and the rolled sheet is the smallest.The aging and homogenization heat treatments extend the range of thermal processing parameters of the AZ61Ce hot rolled sheet.In addition,the aging process significantly reduces the size of the DSA area.