纳米晶体铝在单轴拉伸下的位错堆积对微裂纹扩展的影响

摘要：针对纳米晶体材料，研究了单轴拉伸载荷作用下纳米晶体铝中的裂纹与裂纹尖端发射的位错所形成的滑移面之间的相互作用。通过分布位错法，将裂纹和滑移面等效为均匀分布的连续位错，获得了裂纹面上应力场。并引入裂纹尖端的无位错区，研究了裂纹尖端无位错区对微裂纹的萌生和主裂扩展之间的影响。结果表明，不考虑裂纹尖端无位错区时，裂纹长度较短，会先在晶界处形成微裂纹，主裂纹较长时，主裂纹会直接穿晶扩展。滑移面与裂纹尖端夹角较大时，会增加裂纹尖端发射的位错个数，从而抑制主裂纹的扩展。考虑裂纹尖端无位错区时，无位错区先于晶界处出现微裂纹，通过主裂纹与微裂纹之间位错的相互发射，导致裂纹与尖端处微裂纹汇合，有效加速了主裂纹的扩展。

The Effect of Dislocation Stacking Under Uniaxial Tension on Microcrack Growth in Metallic Crystals

Abstract:TFor nanocrystalline materials, the interaction between cracks in nanocrystalline aluminum and slip surfaces formed by dislocations emitted from crack tips under uniaxial tensile loading is studied.By using the distributed dislocation method, the crack and slip surface are equivalent to the uniformly distributed continuous dislocation, and the stress field on the crack surface is obtained.The effect of dislocation free zone on the initiation and propagation of the microcrack is studied by introducing the dislocation free zone at the crack tip.The results show that the crack length is short without considering the dislocation free zone at the crack tip, and the microcracks will be formed at the grain boundary first, and the main crack will directly penetrate the crystal when the main crack is longer. When the angle between slip surface and crack tip is large, the number of dislocations emitted at the crack tip will be increased, thus inhibiting the propagation of main crack.When the dislocation free zone at the crack tip is considered, the microcracks appear in the dislocation free zone prior to the grain boundary. The mutual emission of dislocations between the main crack and the microcracks leads to the convergence of the crack and the microcracks at the crack tip, which effectively accelerates the propagation of the main crack.