从同一块纯铝双晶体截取试样，分别垂直或平行于其晶界面进行对称拉压疲劳实验．结果发现，在这两种加载方式下，晶界在晶体交变形变损伤断裂过程中的作用及机制有明显区别，横向晶界在变形过程中形成明显的不均匀形变带及多层次的影响区，比较容易萌生裂纹，而纵向晶界变形极小，只发现沿主滑移带的变形及微裂纹形核．相比之下，晶界结构（如∑值）对其自身损伤及裂纹萌生的作用则较弱．同时，对比试样实验结果还显示，相邻晶粒取向软硬相差较大的晶界，以及相对于应力轴的倾斜晶界，均能明显促进晶界疲劳裂纹的生长．
Fatigue tests were performed on specimens P(horizontal grain boundary) and V(vertical grain boundary) which were cut from the same aluminum bicrystal but their orientations are vertical to each other.It is shown that there are remarkable differences in the deformation behaviour and failure mechanisms between specimens P and V.In specimen P,more than two secondary slip systems are activated and primary slip band is repressed in the grain boundary effect zone,it is found that microcracks initiate along grain boundary where deformation is more severe than that in slip band and not uniform. In specimen V,however,the deformation at grain boundary is very small,it can be seen that damage occur only in primary slip bands which reach grain boundary.By considering the same grain boundary structures in specimens P and V,it seems that the effects of grain boundary structure(e.g.∑ value) on the deformation of grain boundary itself are less important.In addition,contrast experiments were done,and it is found that the fatigue cracks growing along the oblique grain boundary and the grain boundary with greater orientation difference between neighboring grains can be obviously accelerated.
参考文献
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| [7] | LimLC,RajR．ActaMetall,1984 |
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