应变量对Al-1Mn-1Mg合金热变形行为的影响

Influence of Strain on the Hot Deformation Behavior of Al-1Mn-1Mg Alloy

在Gleeble热模拟试验机上对不同处理状态(熔体处理与均匀化退火)的Al-1Mn-1Mg合金进行高温压缩试验,通过流变应力曲线分析,重点探讨了应变量对热变形材料常数的影响,并用光学显微镜、透射电子显微镜研究铝材的热变形组织特征。结果表明:经不同处理的Al-1Mn-1Mg合金均易发生动态软化并最终呈现稳态流变特征;热变形材料常数是过程量,随应变量的增加,应力水平参数α、应变速率敏感性指数m和热变形激活能Q随之增大,而应力指数n则逐渐减小;均匀化退火后,铝合金的α和m值最大而n值最小,动态软化效果最明显且变形均匀,在该状态下,铝合金的Q值受变形量影响小,平均仅为176.5kJ/mol,易进行热变形;当应变量为0.7时,基体呈现规则的再结晶晶粒组织,随着应变量的增加,晶内重新形成了位错胞结构。

Compression test at elevated-temperature of Al-1Mn-1Mg alloy prepared by different treatments （melt-treatment and homogenization） was carried out with the aid of Gleeble 1500 thermal simulation machine. The effects of strain on material constants of hot deformation were discussed emphatically by analyzing the feature of flow stress curves, and the hot deformation microstructure of aluminum alloy was studied by OM and TEM. The results show that dynamic softening is easy to occur in these ingots and flow stress becomes steady finally; the material constants of hot deformation are procedural parameters that stress-level coefficient α, strain rate sensibility exponent m and deformation activation energy Q are all increased with strain increasing, while stress exponent n is decreased gradually; the values α and m of the alloy homogenized are the biggest and the value n is the smallest, dynamic softening effect of the alloy is the most obvious, which can deform evenly; influence of strain on the value Q of the alloy homogenized is a little and the average value of Q is only 176.5kJ/mol, so the alloy is easy to deform; the alloy matrix shows the regular recrystallization grains when the strain is 50% dislocation cell structure re-formed in the grains with increase of strain.