单晶Ni_3Al裂纹扩展的TEM原位观察

利用透射电镜（ＴＥＭ）原位拉伸在室温下对（１１０）［１１０］取向 Ｎｉ３ＡＩ合金单晶中裂纹的萌生与扩展进行了研究结果表明：裂纹沿之字形路径扩展且裂纹的总体扩展路径与拉伸轴平行迹线分析表明，首先激活的是（１１１）和（１１１）两个主滑移面上的滑移系；其后在 Ｓｃｈｍｉｄ因子为零的两个滑移面上的滑移系激活．为了解释所观察到的现象而建立了一个位错塞积模型位错应力场的计算表明，塞积位错列所产生的应力场导致了第二滑移系的启动，并使得裂纹扩展路径平行于拉伸轴的方向

IN SITU TEM INVESTIGATION OF CRACK PROPAGATION IN SINGLE CRYSTAL Ni3Al

The initiation and propagation of cracks in (110)[110] oriented Ni3AI alloy single crystals have been investigated by in site tension in TEM at room temperature. The results show that crack propagation appears to be in a zigzag manner and the main crack propagation orientation is along the direction of the tensile axis. The trace analysis shows the two major slip planes, (111) and (111) are activated firstly, and then the other two primary slip planes, (111) and (111) are activated. A model was proposed to explain the observed results. The calculated result of the stress fields shows that the choice of the secondary slip system is dictated by stress concentration which arises from the dislocation pile--up and makes the main crack propagation orientation parallel to the tensile axis.