Characterization of low-temperature superplasticity in a thermomechanically processed TiAl based alloy
Characterization of low-temperature superplasticity in a thermomechanically processed TiAl based alloy
复制标题
DOI：
10.1016/s0921-5093(01)01646-x
复制
发表时间：
2002-06
期刊：
影响因子：
6.4
通讯作者：
Jiangwei Sun;Y. H. He;J. Wu
中科院分区：
文献类型：
--
作者：
Jiangwei Sun;Y. H. He;J. Wu
本文研究了TiAl基合金在低温（750 ~ 900°C）和应变速率（2×10 - 5 ~ 2×10 - 4s-1）下的超塑性。为了细化晶粒，采用两步锻造技术进行材料处理，锻造后不进行后续退火。拉伸伸长率在150 ~ 533%之间。在真应力-应变曲线上的大范围应变硬化与变形过程中高密度的移动的位错有关。测得的激活能为220 kJ mol− 1，接近位错管扩散的激活能。通过光学显微镜和透射电镜观察了超塑变形后的显微组织演变，并与力学性能进行了关联。在此基础上，提出了低温超塑性的主要机制分别是低应变下的晶界滑移和高应变率下的位错滑移蠕变。
Superplasticity of a TiAl based alloy at low temperature ranging from 750 to 900°C and at strain rates from 2×10−5to 2×10−4s−1is characterized in this work. In order to refine the grains, two-step forging techniques were applied for materials processing without subsequent annealing after forging. The tensile elongations between 150 and 533% were obtained. An extensive strain hardening on the true stress-strain curves is linked to the high dense mobile dislocations during deformation. The activation energy of 220 kJ mol−1was measured which is close to the activation energy of dislocation pipe diffusion. Evolution of the microstructures after superplastic deformation were also performed by optical microscope and transmission electron microscope to correlate the mechanical properties. Based on these studies, it is suggested that the predominant mechanism for low temperature superplasticity is grain boundary sliding at low strain and dislocation glide creep at high strain rates, respectively.