γ-TiAl片层界面在裂纹形核中的双重作用

Twofold effects of lamellar interface on crack nucleation in fully lamellar TiAl based alloy

通过全片层γ TiAl基合金SEM原位拉伸实验以及对裂纹前方滑移面及解理面上的应力进行有限元计算 ,研究了片层界面在形核中的作用。当原裂纹与片层平行时 ,裂纹尖端滑移系的分切应力较小 ,滑移相对困难 ,片层面上的正应力比其它解理面上的正应力大 ,从而解理裂纹优先沿片层界面形核 ;当裂纹与片层界面垂直时 ,裂纹尖端很多滑移系上的分切应力较大 ,滑移相对容易 ,片层面上的正应力远比其它解理面上的正应力小 ,从而裂纹优先在跨γ片层的解理面上形核 。

The twofold effects of lamellar interface on crack nucleation in fully lamellar TiAl based alloys were investigated through in situ SEM technique and stress analysis on cleavage planes using finite element method. When the crack is parallel to the lamellae, the resolved stresses on all slip planes ahead of crack tip is small, which makes the slips difficult; while the normal stresses on lamellar interfaces is higher than those on other cleavage planes, which results in crack nucleation along lamellar interfaces preferentially. When the crack is perpendicular to the lamellae, the resolved stresses on many slip planes ahead of crack tip are much higher compared with the condition when the crack is parallel to the lamellae, which makes slips easy; while the normal stresses on lamellar interfaces are much smaller than those on other cleavage planes, which results in crack nucleation along trans lamellar interfaces preferentially, and the lamellar interface is the hindrance of slip and crack propagation. [