Cyclic deformation mechanism of a high-Nb TiAl alloy at high temperature
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摘要: 在750℃下对近片层Ti-45Al-8Nb-0.2W-0.2B-0.1Y合金进行了静拉伸和循环变形，观察和分析变形后试样的微观组织.合金在750℃时的循环应力-应变曲线位于静拉伸应力-应变曲线之上，显示出明显的循环硬化特征；在循环变形过程中呈现先硬化后稳定.透射电镜观察显示，在750℃下循环变形和拉伸的合金试样中均发现有大量的位错钉扎、塞积及缠结存在，而形变孪晶仅在循环变形后的合金试样中存在.合金在750℃下的循环变形中孪生起重要作用.Abstract: Tension and cyclic deformation tests of a nearly lamellar Ti-45Al-8Nb-0.2W-0.2B-0.1Y alloy were carried out at 750℃, and the corresponding microstructures were examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It is found that the cyclic stress-strain curve of the alloy at 750℃ is above the static tensile curve, indicating an obvious cyclic hardening characteristic of the alloy at 750℃;the cyclic stress-strain behavior of the alloy is characterized by first hardening and then stabilization. TEM observations show that there are lots of dislocation pile-ups, pinnings and tanglings in cyclic deformation and tensile specimens, but large amounts of mechanical twinnings only occur in the former, implying that twinnings play a considerable role in the cyclic deformation process of the alloy at 750℃.
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