Ti_3Al基合金的热变形行为及加工图

Deformation Behavior and Processing Map of Ti_3Al Based Alloy during the Isothermal Compression

采用THERMECMASTER-Z热模拟试验机对Ti3Al基合金进行等温恒应变速率压缩试验,基于动态材料模型的加工图技术研究该合金在950～1350℃和0.001～10s-1范围内的高温变形特性,并优化出其适宜的高温变形参数范围。结果表明,在应变速率较高(≥0.05s-1)时,变形多处于失稳区域。在变形温度为950～1100℃,应变速率为0.05～10s-1区域,发生了绝热剪切和局部流动现象;在变形温度为1100～1350℃,应变速率为0.1～10s-1区域发生了β组织的不均匀变形。在变形温度为1250～1350℃,应变速率低于0.01s-1时,变形组织粗大,其变形机制为动态回复。在变形温度为1100～1180℃,应变速率为0.001～0.015s-1时,功率耗散效率多大于0.55,变形组织中出现了亚晶;在温度为970～1010℃,应变速率为0.001～0.01s-1时,功率耗散系数大于0.5,其变形机制可能为超塑性成形,这2个区域为Ti3Al基合金适宜的热变形工艺参数范围。

The isothermal constant strain rate compression tests of a Ti3Al based alloy were conducted by THERMECMASTER-Z simulator and the deformation behavior at the temperature of 950-1350 oC and strain rate of 0.001-10 s-1 were investigated. The processing maps under these deformation conditions were constructed and the hot working parameters were then optimized based on the generated processing maps. The processing maps developed on the basis of dynamic material model exhibit following five domains. （1） The alloy exhibits domain of flow localization and adiabatic shear bands in the temperature range of 950-1100 oC and strain rate range of 0.05-10 s-1. （2） The region of flow instability occurs in the temperature range of 1100-1350 oC and strain rate range of 0.1-10 s-1. The manifestation of flow instability is non-uniform deformation of β grains. （3） The alloy undergoes dynamic recovery in the temperature region of 1250-1350oC and a strain rate below 0.01 s-1. The materials exhibit significant grain coarsening in this domain. （4） The subgrain could be found in the temperature range from 1100 oC to 1180 oC and the strain rate from 0.001 to 0.015 s-1 with a power dissipation efficiency above 0.55. （5） The deformation characteristic of the Ti3Al based alloy in the temperature ranger of 970-1010 oC and strain rate range of 0.001-0.01 s-1 is superplasticity with power dissipation efficiency above 0.5. The last two regions can be considered as the optimal parameter range of isothermal compression for Ti3Al based alloy.