在ＴＥＭ下原位观察了双相ＴｉＡｌ层状组织对裂纹扩展的影响，发现裂纹尖端的钝化以及裂纹的扩展方式与裂纹和片层界面的夹角有关。当裂纹接近平行片层界面时，主裂纹前端有微裂纹产生，此时剪切带韧化机制起主导作用。而当裂纹垂直于片层界面以及介于平行与垂直之间时，片层界面对扩展裂纹的阻碍、界面滑移造成的裂纹尖端钝化是层状组织韧化ＴｉＡｌ合金的主要原因。依据裂纹形核的位错理论对上述现象进行了分析。
In situ TEM technique was employed to observe the influence of lamellar structure on the crack propagation in duplex TiAl alloy. It has been found that both crack tip blunting and crack propagating have connected with the angle included between crack growth and lamellar direction. Only if the crack growth roughly parallel to lamellar direction ,the microcracks may nucleate ahead of the main crack. So, shear ligaments play an important role in toughening TiAl alloy. When the crack growth is perpendicular to lamellae or between perpendicular and parallel to lamellae, the main reasons of lamellar toughening in TiAl alloy owe to that:(1) the lamellar boundary inhibits crack propagation,and(2)the crack tip blunting is caused by the slip of interlamellar boundary. According to the dislocations theory of microcrack nucleation, these phenomena are explained.Correspondent: LIN Dongliang, professor,(Shanghai Jiaotong University, Shanghai 200030)
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