本文报道了α-Ti拉伸裂纹成核和扩展的高压电镜动态观察的实验结果,完整地观察到位错运动导致滑移带两端形成滑移台阶,由于应力集中,在滑移台阶处裂纹成核,并在应力作用下扩展。裂纹扩展有两种方式:(1)在应力作用下裂纹尖端塑性区减薄,裂纹以不连续的方式沿着减薄区扩展;(2)主裂纹与其前端的微裂纹或孔洞联结导致扩展。文章还指出,在α-Ti中晶界可能不是裂纹成核的择优地点和裂纹扩展的优先路径。
This paper presents the results obtained from the in situ observations of the crack nucleation and its propagation under tensile loading in HVEM. It was found that some slip bands appeared and slip steps formed at both ends of a slip band through the movement of a great deal dislocations. The crack is initiated at the slip step owing to the stress concentration. Once a crack has nucleated, it will propagate forward under the applied stress. The cracks propagate essentially in two ways: (1) during tensile loading, a large plastic thinning zone is formed near the crack tip. The crack propagates along the thinning zone with a discontinuous manner; (2) the main crack propagates by a mechanism of coalescence of microcracks in the vicinity of the crack tip. Additionally, it was noticed that the grain boundary is not probably the preferential sites of the crack nucleation and propagation in α-titanium.
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