陶瓷刀具材料断口形貌及裂纹扩展的分形特征

Fractal characteristic of the fracture morphology and crack propagation of a ceramic tool material

通过热压烧结工艺,制备了一种高性能的Si3N4基陶瓷刀具材料。利用X射线衍射仪和扫描电子显微镜分别对材料物相组成、微观形貌及裂纹扩展路径进行了分析。借助图像处理技术和分形理论,计算了断口形貌及裂纹扩展路径的分形维数,并揭示材料断裂机制。研究表明,Si3N4基陶瓷刀具材料表现为穿晶/沿晶的混合断裂模式,其裂纹扩展方式主要是偏转和桥联,断口形貌及裂纹扩展均具有明显的分形特征。当材料断口形貌越粗糙,裂纹扩展路线越不规则,分形维数值增大,表明断口微观结构的粗糙程度、裂纹扩展路线的不规则程度可用分形维数来刻画。

A Si3N4 ceramic tool material with high mechanical properties was prepared by hot-pressing sintering process.The phase identification,fracture surface microstructure and crack propagation path were characterized by X-ray diffraction(XRD)and scanning electron microscopy(SEM).By means of image processing technique and fractal theory,the fractal dimension of fracture morphology and crack propagation path was calculated,and the fracture mechanism of the ceramic material was revealed.The results show that the Si3N4 ceramic material shows a mixed fracture mode of transgranular and intergranular,and the main mode of the crack propagation was deflection and bridging.The fracture morphology and crack propagation path of the material have an apparent fractal characteristic.With the increase of the fractal dimension,the fracture morphology shows more complex,and then the crack propagation path was more irregular.It was indicated that the complexity of microstructure and the irregularity of crack propagation can be described by fractal dimension.