Journal of the Society of Materials Science, Japan
Online ISSN : 1880-7488
Print ISSN : 0514-5163
ISSN-L : 0514-5163
Molecular Dynamics Simulation of Deformation-Induced Nanocrystallization in an Amorphous Metal
Ryosuke MATSUMOTOHiroshi KITAGAWAAkihiro NAKATANI
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2003 Volume 52 Issue 3 Pages 235-240

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Abstract

A large-scale molecular dynamics simulation is performed to obtain fundamental knowledge of deformation-induced nanocrystallization in an amorphous metal. The Finnis-Sinclair potential is adopted to represent α-iron. The model amorphous metal is created by a heating-rapid quenching simulation. Tensile deformation is applied to the amorphous block with 512 026 atoms. The initial temperature is 300K. As it is deformed severely, a lot of nucleationsites of crystal-clusters are observed around the shear bands which develop in the direction of about 45 degrees from tensile direction. The nucleation temperature of crystal is about 1200K which is about a half of glass transition temperature. The average distance between any two nucleation sites is about 6nm. Those clusters grow up rapidly until they strike each other. In the process, deformation is localized at the remaining amorphous phase, because the grains are rarely deformed. Some large grains grow bigger by absorbing small grains, therefore the total number of grains decreases. After the nanocrystallization, deformation twins are observed in some grains. At the final stage of deformation, a void is nucleated at a grain boundary. The crystalphase develops by latent heat of crystallization even after a break. Dislocations which are packed in the grain are moved out to the grain boundary or amorphous phase immediately. Grains whose (111) directions turn on the tensile direction are rarely nucleated. Some grains have long shape, because they nucleate beside the shear bands and grow toward low temperature regions.

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