Molecular-dynamics Study on Fracutre Property of Amorphous Metal with Crystallization

The fracture property of amorphous metal was studied by a large scale molecular dynamics (MD) simulation. The Finnis-Sinclair potential for α-iron was used as an inter-atomic potential. At first, we made a model amorphous metal by melting-rapid quenching simulation. And then a crystal growth simulation in the amorphous was performed. We used circular model, and the cracktip is assumed to be at the center. In order to analyze the crack growth characteristics in an infinite domain, the linear elastic solution of Mode I crack was used as a boundary condition. The periodic boundary condition was used to the thickness direction. The crack opens in similar fashion and it has smooth surfaces during the amorphous state. As it deformed, some clusters of bcc-crystal nucleate around the cracktip and they grow rapidly. The distribution of deformation zones and deformation mechanism are significantly altered. The grains are not deformed while they are relatively small. The emission of dislocations from the cracktip is observed, after the crystal phase covered the crack-tip surfaces. The grain size appeared small in the vicinity of the crack-tip, and becomes gradually large as it separates form the crack-tip.