Atomistic Analysis of Crack Propagation in Amorphous Metal.

Abstract

Large scale molecular dynamics simulation are performed to examine the fracture mechanism of an amorphous metal. Crack propagation properties in a model amorphous material made from FS-potential for Fe atom are analyzed for a thick-plate model with periodic structure and a thin-plate model. In the former model, being promoted by development of band-like shear deformation emanating from the crack tip and density decrease in the crack front region, smooth crack blunting with round tip proceeds. On the other hand in the thin plate model, after blunting slightly, the crack sharpening proceeds, which is accompanied by a narrow damaged region in the crack front where a void nucleates thereafter. And coalescence of the crack and void drives further crack advance. Fracture in amorphous metal is revealed to be ductile locally but brittle-like macroscopically, which are quite different from those in the materials with crystalline structure.