材料期刊网

对Ti-45Al-8Nb-0.2Si-0.3B(原子分数, %)合金进行热压缩实验, 采用基于动态材料模型建立的加工图研究了在变形温度为950-1300 ℃, 应变速率为0.001-10 s^-1条件下的热变形行为. 结果表明: 在热压缩过程中, 高Nb-TiAl合金在不同变形温度和应变速率下表现出不同的流变行为. 该合金在温度为950-1200 ℃, 应变速率为1-10 s^-1 和温度为1250-1300 ℃, 应变速率为10 s^-1 两个区域内易产生流变失稳现象. 在温度为 950-1100 ℃, 应变速率为0.1-0.001 s^-1的区域和温度为1250-1300 ℃, 应变速率为0.001-1 s^-1的区域内合金发生了动态再结晶. 在动态再结晶区域内功率耗散效率在40%-55%之间, 热变形后组织细小均匀. 该合金的功率耗散效率的峰值区为1150-1200 ℃, 应变速率为0.001 s^-1, 峰值效率为64%, 在此区间内合金发生超塑性变形.

The hot deformation behavior of a high-Nb-containing TiAl based alloy has been studied using the processing map approach. Compression tests were conducted in the temperature range of 950-1300 ℃ and the strain rate range of 0.001 s^-1  to 10 s^-1 on a Gleeble-3800 testing system. The flow stress was found to be strongly dependent on the temperature and the strain rate. The regimes of flow instability have been delineated in the temperature range of 950-1200 ℃ and the strain rate ranges from 1 s^-1 to 10 s^-1, as well as in the temperature of 1250-1300 ℃ and the strain rate of 10 s^-1. The optimal hot-working conditions for the investigated TiAl alloy are in two regimes: (i) in the temperature range 950-1100 ℃ and at the strain rate of 0.001 s^-1 to 0.1 s^-1, and (ii) in the temperature range 1250-1300 ℃ and at the strain rate of 0.001 s^-1 to 1 s^-1. The material exhibited dynamic recrystallization to produce a fine-grained microstructure in these conditions. In the temperature range 1150-1200 ℃ with the strain rate 0.001 s^-1, the alloy exhibited superplasticity.