采用Gleeble-1500D热模拟试验机对ZK60和ZK60-1.0Er镁合金进行了热压缩实验,分析了合金在温度为160～420℃,应变速率为0.0001～1.0s-1条件下的流变应力变化特征.结果表明:两种镁合金在热压缩过程中的流变应力随变形温度的降低和应变速率的升高而增加,在流变应力达到峰值后随即进入稳态流变;稀土Er的加入使得平均变形激活能Q值由183kJ/mol降到153kJ/mol,应力指数n值由6提高到8;发生动态再结晶的临界应力σc值随变形温度升高和应变速率降低而降低,在420℃/1.0s-1高温高应变速率时,稀土Er的加入使得ZK60镁合金发生动态再结晶的临界应力值σc由76MPa降到50MPa.通过动态模型构建热加工图并结合金相组织观察可知:稀土Er的加入缩小了ZK60镁合金的热加工失稳区,增加了热加工安全区的功率耗散效率峰值ηmax,由35％增大到45％,促进了动态再结晶晶粒的形核,但抑制了再结晶晶粒的长大.
The hot compressive deformation behavior of ZK60 and ZK60-1.0Er magnesium alloy occurring homogenization was investigated by Gleeble-1500D thermal simulator,analyzing the characteristics of the flow stress changes of the two kinds of magnesium alloys at the temperature 160-420℃,the strain rate 0.0001-1.0s-1.The experimental results show that the two kinds of magnesium alloys are deformation temperature and strain rate sensitive materials,with the decrease of deformation temperature and the increase of strain rate,the flow stress increases;meanwhile,flow stress value tends to be constant after flow stress reaches peak value.Rare earth Er reduces the average deformation activation energy from 183kJ/mol to 153kJ/mol,and the stress index n value is improved from 6 to 8;dynamical recrystallization critical stress σc value decreases,with the increase of deformation temperature and the decrease of strain rate,and at 420℃/1.0s-1,rare earth Er reduces the critical stress σc value of occurring dynamic recrystallization from 76MPa to 50MPa.According to the obtained processing map by material dynamic model,combining with microstructure observations,rare earth Er reduces instability areas of ZK60 magnesium alloy,and increases power dissipation efficiency value ηmax from 35 ％ to 45 ％ at safety zone,promotes dynamic recrystallization grain nucleation,but inhibits recrystallization grain growth.
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