挤压Mg-4.5Zn-0.75Y合金的热变形行为

为了研究只含准晶相Mg-Zn-Y合金的高温力学性能并获得其较优的加工参数,本文首先制备了含有I-Phase的挤压Mg-4.5Zn-0.75Y(原子数分数/%,下同)合金,并在Gleeble-3500热/力模拟实验机上对其高温变形行为进行了研究,实验温度为300、350、400℃,应变速率为0.01、0.1、1 s~(-1).在此基础上,建立了该合金的流变应力本构方程及DMM加工图,并结合压缩后的显微组织制定较优的加工工艺参数.结果表明:应变速率和加工温度对流变应力有显著的影响;挤压Mg-4.5Zn-0.75Y合金的平均变形激活能和应力指数分别为107.95 kJ/mol和3.996 6;挤压Mg-4.5Zn-0.75Y合金具有较好的热塑性,在实验条件下并没有发生失稳现象,说明准晶相的存在提高了合金的变形能力;压缩后的显微组织显示,当温度为300~350℃、应变速率0.1~1s~(-1)时,合金压缩后为均匀细小的等轴晶;综合Mg-4.5Zn-0.75Y合金的加工图与压缩后的显微组织图,确定了该合金热加工的较优工艺参数为:θ=300~350℃;ε·=0.1~1s~(-1).

Hot deformation behavior of extruded Mg-4.5Zn-0.75Y alloy

In order to investigate the mechanical properties of Mg-Zn-Y alloy which only contains quasicrystal phase at evaluate temperatures,and to obtain the optimal processing parameters,an extruded Mg-4.5Zn-0.75Y (at％) alloy was produced firstly.And then,hot compression deformation behavior of the extruded Mg-4.5Zn-0.75Y alloy was investigated at temperatures ranging from 300 ℃ to 400 ℃ and strain rates ranging from 0.01 s-1 to 1 s-1 by Gleeble-3500 thermal/mechanical simulator.Meanwhile,a constitutive equation and processing map were developed to describe the flow characteristics.Notably,the microstructures of the experimental alloy were observed to obtain optimal deformation parameters.The results show that the strain rate and deformation temperature exert remarkable influences on the flow stress.The average activation energy and the stress exponent of deformation are 107.95 kJ/mol and 3.996 6,respectively.There is no flow instability region in the processing map,which shows that the extruded Mg-4.5Zn-0.75Y alloy has good thermoplastic under the experimental conditions and the exist of quasicrystal phase is good for its plastic deformation.Microstructures of the compressed samples show that uniform and fine equiaxed grains were obtained when the parameters were 300 ～ 350 ℃ and 0.1 ～ 1 s-1.Based on the rnicrostructure observation and processing map,the optimal hot working conditionals are determined to be temperature of 300～350 ℃ and strain rates of 0.1～1 s-1.