FeMoSiB纳米晶薄带的裂纹扩展阻力和结构的关系

STUDY ON THE MICROSTRUCTURE-FRACTURE RESISTANCE RELATIONSHIP OF FeMoSiB NANOCRYSTALLINE RIBBON

通过对不同晶粒尺寸的ＦｅＭｏＳｉＢ纳米晶的断裂韧性的测量和断裂行为的分析，研究了纳米晶结构和裂纹扩展阻力之间的关系．ＦｅＭｏＳｉＢ纳米晶的断裂模式是沿晶断裂，造成了很小的裂纹扩展阻力．裂纹扩展阻力随晶粒尺寸增加而增加，其中的韧化机制是裂纹扩展过程中晶粒团的桥接和拔出摩擦作用．根据纳米晶的结构特点认为裂纹扩展阻力将会达到一个极大值，然后由于内应力的作用而下降．而裂纹扩展阻力随晶粒尺寸的变化与塑性变形基本没有关系．

Through the fracture toughness measurements and analyses of fracture morphologies of FeMoSiB nanocrystalline with various grain sizes, the microstructure-fracture resistance relationship has been investigated. It was proposed that low fracture resistance can be attributed to intergranular cracking. Fracture resistance increases with the grain size from 11 to 35 um. And grain blocks' bridging and interfacial friction are the major toughening mechanism. Fracture resistance will reach a maximum and are expected to fall over at larger grain size due to internal stress induced microcracking. Furthermore, variation of fracture resistance with grain size is proposed to be independent of plastic deformation over the grain size range concerned.