纳观尺度下不同晶向取向对裂纹萌生和扩展的影响

Study on the Effect of Different Crystal Orientations on Crack Initiation and Propagation at Nano Scale

【目的】了解裂纹的生长特征和扩展规律,揭示纳米级裂纹扩展机理及其对材料断裂的影响。【方法】采用晶体相场法研究不同初始晶向倾角在y方向单轴拉伸作用下裂纹扩展演化、对应的应力分布及其应力曲线。【结果】当拉应变作用达到临界值时,无预应变的样品裂口开裂方式不同。5°与20°晶向倾角的样品裂口直接开裂,并伴随着位错出现。10°与15°晶向倾角的样品裂口先发射位错,裂口准备开裂。裂纹形成后,5°与20°晶向倾角的样品裂纹主要呈脆性断裂模式扩展。10°与15°晶向倾角的样品为典型的韧性断裂模式扩展。【结论】不同晶向倾角对裂纹萌生时间、扩展方向以及韧-脆扩展形式有重要影响。

【Objective】To understand the growth characteristics and expansion laws of cracks can help to reveal the mechanism of nano scale crack propagation and its effect on material fracture.【Methods】The crystal phase field(PFC)method is used to study the crack propagation evolution diagram,the corresponding stress distribution diagram and the stress curve diagram of different initial crystal tilt angles under uniaxial tension in the y direction.【Results】When the tensile strain reaches a critical value,the cracking mode of the sample without prestrain is different.The crack of the sample with a 5°and 20°crystal tilt angle directly cracks and is accompanied by dislocations.The crack of the sample with a 10°and 15°crystal tilt angle first emits dislocations,and the crack is ready to crack.After crack formation,the cracks of the sample with 5°and 20°crystal tilt angles mainly expand in the brittle fracture mode.The samples with 10°and 15°crystal orientation were typical ductile fracture mode.【Conclusion】Different crystal orientation angles have an important influence on crack initiation time,propagation direction and ductile-brittle expansion.