温度对体心立方钼中位错行为影响的原位透射电镜研究

温度对体心立方钼中位错行为影响的原位透射电镜研究

严靖园，余  倩^*

（浙江大学电子显微镜中心，硅材料国家重点实验室，材料科学与工程学院，浙江杭州310027）

摘 要  本文通过原位透射电镜下的拉伸试验，在不同温度下研究了具有室温韧脆转变行为的体心立方钼中的位错行为。结果表明，室温下钼的变形过程中主要以刃位错和混合位错的运动为主，位错运动受扭结对机制控制，存在大量刃位错的快速运动和螺位错交滑移行为，位错运动情况复杂。低温下，刃位错运动被抑制，螺位错运动为主导变形行为。螺位错以长直形态存在，以非连续跳跃方式运动。这种低温下活跃的螺位错行为以及温度与位错行为变化的关系尚无法用传统热激活理论解释，声子拖拽机制或变为位错运动的激活机制。

关键词   原位电镜；体心立方；位错行为；低温变形

中图分类号：TG13；O77；TG115.21⁺5.3  文献标识码：A      doi:10.3969/j.issn.1000-6281.2020.04.001

In situ TEM investigation of the temperature dependence of dislocation behavior of BCC molybdenum

YAN Jing-yuan，YU Qian^*

( Center of Electron Microscopy，State Key Laboratory of Silicon Materials，and School of Material Science and Engineering，Hangzhou Zhejiang 310027，China)

 Abstract  The dislocation behavior of molybdenum with room-temperature ductile-brittle transition behavior in different temperatures was studied by in situ straining in TEM. It was found that at ambient temperature, the deformation was dominated by the motion of edge and mixed dislocations, which was controlled by the kink-pair mechanism. Rapid motion of edge dislocation and extensive cross slipping were found at ambient temperature, which indicated the convoluted dislocation behavior at this temperature. In low temperature, the motion of edge dislocation was depressed while screw dislocation dominate the deformation. The screw dislocations were long and straight, moving in a jerky and lock-unlock mode. The active movement of screw dislocations and the relationship of dislocation behavior and temperature couldn’t be explained by classical rules of thermodynamics, and the phonon drag mechanism might become the dominant dislocation activation mechanism.

Keywords  in situ TEM；body-centered-cubic；dislocation behavior；low-temperature straining

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