Mechanical Properties of Amorphous Metal with Dispersed Nanocrystalline Particles: Molecular Dynamics Study on Crystal Volume Fraction and Size Effects

Abstract

Large-scale molecular dynamics simulations of tensile deformation of amorphous metals with nanocrystalline particles were performed in order to clarify the effects of particle size and crystal volume fraction on the deformation property and the strength. It was clarified that the size effects of the particle are very small, whereas the influences of the crystal volume fraction are large. Young’s modulus and the flow stress become large as the crystal volume fraction increases. Even after the yielding of the amorphous phase, the stress of the crystal phase still continues to increase. Thus, the flow stress of the composite increases after yielding, which prevents plastic localization and improves the ductility. When the crystal volume fraction is small, the stress distribution is homogeneous in the particle including near the amorphous-crystal interface. Therefore, possibility of deformation is small, and inside-particle plastic deformation is negligible. When the crystal volume fraction is high, the particle undergoes plastic deformation even with small global deformation. After the yielding of the crystal particle, the flow stress decreases because defects are introduced into the crystal. It is expected that there is an ideal crystal volume fraction that gives the maximum ductility. A Lennard-Jones potential modified to enforce the continuity at the cut-off distance was used as an interatomic potential. The potential parameters were defined based on Inoue’s three basic principles.