借助扫描电镜(SEM)原位拉伸观察了纯钼退火态纤维状组织断裂过程中裂纹萌生与扩展的动态变化过程,对其微观断裂特征进行了研究.结果表明:加载初期,裂纹在与最大主应力平面成45°的位置萌生,随后逐渐张开并钝化;加载中期,新的裂纹在钝化的主裂纹前方某处萌生.随着载荷增加,裂纹呈"Z"字形相互连接;加载末期,裂纹失稳扩展,试样断裂.在裂尖应力场作用下,裂纹扩展遵循钝化-萌生-钝化的循环方式.纯钼试样断裂后,沿厚度方向有明显的颈缩,断口表面呈薄层状纤维撕裂,并伴有剪切唇和韧窝的出现,呈延性断裂特征.
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