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1·Their toughening mechanisms were fine-grain toughening, crack deflection, crack branching and crack microbridging.

韧化机制为细晶韧化、裂纹偏转、裂纹分支和微桥接。

2·Consequently, at the macroscopic crack branching velocity, the experimental fracture surface energy and the fracture surface roughness; have no single value in such materials.

因此，对这种材料在宏观裂纹分叉速度时，实验断裂表面能及断裂表面韧性没有单一值。