Structural relaxation in a model amorphous alloy

Abstract

Structural relaxation of a metal-metal-type amorphous alloy has been simulated using the method of molecular dynamics for a model Cu57Zr43 alloy constructed by central force interatomic potentials. The sharpening of the peaks in the total radial distribution function (RDF) after annealing agrees well with that of experiment. The decrease of the internal energy Delta E is related to the density change Delta rho by the equation - Delta E/ mod E mod =1.6 Delta rho / rho , which means that the structural relaxation is achieved by the densification which increases the average coordination number. The densification is found to occur effectively by developing compositional short-range order (CSRO), i.e. by increasing the number of unlike pairs of the small atom (Cu) and the large atom (Zr). The formation of CSRO causes the shift of the first peak of the partial RDF (PRDF), outward for Cu-Cu pairs and inward for Zr-Zr pairs, resulting in the sharpening of the total RDF. The atomic diffusion has been found to be quite heterogeneous with a dimension of about five atomic spacings.