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用TEM拉伸方法，对具有fcc结构的304L钢、进行了晶内裂纹萌生与裂纹连续扩展的原位观察．结果表明：晶内开裂时首先形成无位错区．裂纹在无位错区中形成．裂尖扩展和裂尖前晶面变形行为由原位观察和原位选区衍射的结果进行分析．裂纹沿｛100｝晶面扩展时．裂尖前｛100｝晶面发生倾转，｛111｝晶面局部弹性弯曲，裂尖钝化；｛100｝倾转增大以致开裂，钝化裂尖扩展，｛111｝局部弯曲有所恢复．
In-situ observation of crack initiation and crack propagation in 304L steel with fcc structure was carried out by TEM tensile method. The results show that dislocation-free region is firstly formed in the intragranular cracking. Cracks form in the dislocation-free zone. The crack tip extension and the deformation behavior of the crack tip before the crystal plane were analyzed by the results of in situ observation and in-situ diffraction. Crack along the {100} crystal plane expansion. The {100} crystal plane tilted before the crack tip, the {111} crystal plane flexed locally and the crack tip was passivated; the {100} tilt increased so as to crack, the passivated crack tip expanded, the local bending of {111} .