TiAl基合金超塑性变形的力学行为研究  

Mechanical Properties of TiAl Based Alloy during Superplastic Deformation

作　　者：张俊红[1] 徐亚娟[1] 黄伯云[2] 贺跃辉[2] 

机构地区：[1]洛阳理工学院,河南洛阳471023 [2]中南大学粉末冶金国家重点实验室,湖南长沙410083

出　　处：《稀有金属材料与工程》2014年第6期1492-1496,共5页Rare Metal Materials and Engineering

基　　金：国家'863'计划资助项目(715-05-0040)

摘　　要：采用恒应变速率和应变速率递增实验研究了变形态Ti-48Al-2．3Cr-0．2Mo（at％）合金的超塑性变形力学行为，并根据计算得到的变形激活能，结合超塑性变形的流变曲线形态，对TiAl基合金的超塑性变形机理进行了分析。超塑性拉伸试验分别在800～900℃区间和950～1100℃区间和应变速率k=1×10^-3-5×10^-5s^-1的条件下进行。结果表明，变形态TiAl基合金超塑性变形的应变-应力曲线上几乎没有稳态塑性流变阶段。在950～1100℃区间，加工硬化现象显著。当T〉1025℃或ε≤5×10^-4s^-1时，应力-应变曲线呈典型的加工硬化形态，并且随着变形温度升高和应变速率降低，加工硬化阶段增长。原始组织中的高密度位错是引起加工硬化的原因。在800～900℃区间，应变速率敏感性因子m的最佳值在0．52-0．67之间，超塑性变彤的表观激活能为Qapp=178kJ／mol，晶界扩散是超塑性的速率控制机制。在950～1100℃区间，m的最佳值在0．63～0．77之间，超塑性变形的表观激活能值Qapp=290kJ／mol，晶格扩散是超塑性变形的速率控制机制。Superplastic mechanical behavior of Ti-48Al-2.3Cr-0.2Mo （at%） alloy with deformed microstructure was investigated at temperatures ranging from 800 to 1100℃ with strain rates between 5×10^-5 and 1×10^-3 s^-1 by constant strain rate tests and incremental strain rate tests. Depending on the plots of true stress-true strain and the data of activation energy calculated in the tests, the mechanism of superplasticity was discussed. Results show that for the Ti-48Al-2.3Cr-0.2Mo alloy, there is almost no constant stress stage but hardening is observed in the plots of true stress-true strain. Particularly, at the temperatures above 1025 ℃ or strain rates below 5×10^-4 S^-1, a continuous strain hardening stage is observed, and with the increasing of the temperature and the decreasing of the strain rate, the stage increases. High-density dislocation caused by pre-deformation is suggested the reason of hardening. At temperatures from 800 to 900℃, the maximum strain rate sensitivity （m） values are 0.52-0.67, and the activation energy of the alloy is calculated as Qapp =178 kJ/mol, indicating that the dominant mechanism of superplastic deformation is grain boundary siding controlled by grain boundary diffusion. At temperatures from 950 to 1100 ℃, the maximum strain rate sensitivity （m） values are 0.63-0.77, and the activation energy of the alloy is calculated as Qapp =290 kJ/mol, suggesting that the dominant mechanism of superplastic deformation is grain boundary siding controlled by lattice diffusion.

关 键 词：TIAL基合金 超塑性 变形机制 

分 类 号：TG146.23[一般工业技术—材料科学与工程]