Crystallization in an amorphous metal during shear deformation: a molecular dynamics study

A Molecular Dynamics (MD) simulation was performed to investigate the structural changes during a shear deformation process in an amorphous metal. An amorphous model is constructed from 1372 Ni atoms interacting via a Morse type pairwise additive potential. At shear stresses below 2.4 GPa, shear strain increased linearly with increasing shear stress. However, when shear stress reached 2.8 GPa, large shear deformation occurred until the shear strain reached 0.79. During this shear deformation, crystallization was observed in the model. The crystalline phase had an fcc structure which had an orientation relationship, i.e. the shear direction and a (111) plane were parallel. Experimental investigation was also performed using a micro-sized Ni-P amorphous alloy specimen. After bending test, precipitation of crystalline phase which has an fcc structure was observed. Furthermore, crystallographic orientation, obtained from MD simulation, was also confirmed. From these results, the mechanism of crystallization during phase deformation was discussed.