氢对位错行为影响的原位电镜研究

In situ TEM study on the effects of hydrogen on dislocation behavior

氢脆可导致金属材料发生无征兆的断裂,造成安全事故。氢脆最主要的特征是氢致材料损失,而位错是金属塑性变形的主要载体,理解氢对金属中位错行为的影响是破解氢脆微观机制的基础。过去的宏观氢脆实验和事后表征无法直接观察位错行为的变化,因此无法将氢-位错的交互作用从复杂的实验现象中解耦出来单独研究,而近些年来快速发展的原位透射电镜技术使得定量研究氢和单根位错的交互作用成为现实。本文简要综述了美国伊利诺伊大学利用原位透射电镜技术在氢对位错行为影响研究方面的经典工作,分析了该系列工作存在的问题,并介绍了西安交通大学针对这些问题设计的新型原位电镜实验方法,利用该方法可以实现有氢和无氢环境中位错运动的定量对比。实验结果发现,氢阻碍铝的位错运动,却促进铁的位错运动,表明氢对位错的影响与材料类型及位错类型相关。

Hydrogen embrittlement can cause metals to fracture without warning,leading to a safety catastrophe.A key character of hydrogen embrittlement is the reduction of material ductility caused by hydrogen.For metals,dislocations are the primary carriers of plasticity.Studying the effects of hydrogen on dislocation behavior is fundamental to establishing the theory of hydrogen embrittlement.Previous macroscopic experiments and post-characterization method were unable to directly observe the behavior of dislocations,making it difficult to single out the interaction between hydrogen and dislocations from complex experimental phenomena.Recent advances in in-situ transmission electron microscopy technology have render it possible to quantitatively study the interaction between hydrogen and individual dislocations.This paper provides a brief review of classic experimental works on the effects of hydrogen on dislocation behavior conducted by the University of Illinois,and analyzes the issues in this series of works.Additionally,it introduces a new in-situ electron microscopy experimental method designed in Xi'an Jiaotong University to address these issues.This new method enables a quantitative comparison of dislocation motion in the presence and absence of hydrogen.Experimental results demonstrate that hydrogen hinders the dislocation motion in aluminum,while promoting the dislocation motion in iron.