Effect of Nanoscale Amorphization on Edge Dislocation Emission from a Bifurcated Crack Tip in Deformed Nanocrystalline Solids

The effect of nanoscale amorphization at the triple junction of grain boundaries on edge dislocation emission from a bifurcation crack tip in nanocrystalline materials has been suggested and theoretically described. A corresponding mechanical model has been established, and the exact analytical solution of the modified model was obtained using the complex potential method of elastic mechanics. The resultant force acting on the dislocation was calculated, and the analytical expression for the critical stress intensity factor corresponding to dislocation emission was obtained based on the dislocation emission criterion. The influence of the size, position, strength of nanoscale amorphization, and bifurcation crack shape on the critical stress intensity factor was discussed using numerical analysis. The study found that an increase in the angle between the main crack and the branched crack makes it more difficult for dislocations to emit from the bifurcation crack tip. The critical dislocation emission angle is independent of the angle between the main crack and the branched crack. The presence of nanoscale amorphization can reduce the high stress field near the bifurcation crack tip, making it difficult for dislocations to emit from the bifurcation crack tip, thereby reducing the toughness of the material caused by dislocation emission.