An atomistic insight into the fracture behavior of bicrystal aluminum containing twist grain boundaries

摘要

Transgranular fracture in crystalline materials is strongly affected by the presence of twist misorientation of the grain boundaries and the plastic work ahead of the transgranular crack tip. Despite this, the underlying mechanisms associated with crack-twist grain boundary interactions during transgranular fracture remain rudimentary. In view of this, transgranular fracture behavior of precracked bicrystal Aluminum containing (1 1 0) twist grain boundaries is investigated using molecular dynamics simulations within the framework of embedded-atom method. The grain boundaries have been shown to act as both a cleavage as well as dislocation source. The first plastic evolution, if any, always occurs from the grain boundary region ahead of the penetrated crack tip, which is in contrast to the intergranular fracture behavior where dislocations are known to be emitted from both the crack tip as well as grain boundary region ahead of the crack tip. Further plasticity evolution in the neighboring grain that occurs after crack stagnation at the twist grain boundary deters further crack propagation. It is observed that the overall fracture resistance of bicrystal material is inversely related with the grain boundary energy. Consequently, the role of twist grain boundaries in affecting the fracture toughness of crystalline materials during transgranular fracture should not be ignored. (C) 2017 Elsevier B.V. All rights reserved.