Vitrification, crystallization, and atomic structure of deformed and quenched Ni60Nb40 metallic glass

Abstract

A Ni60Nb40 alloy was vitrified from fcc Ni and bcc Nb by cold rolling and by rapid solidification of an alloy ingot. The Ni60Nb40 that was vitrified by rolling has a lower crystallization onset temperature with single crystallization reaction compared to the two-stage crystallization at higher temperature for quenched Ni60Nb40. Fluctuation electron microscopy and hybrid reverse Monte Carlo modeling show that the as-rolled Ni60Nb40 contains fewer icosahedral-like Voronoi clusters and more crystal-like and bcc-like Voronoi clusters, which are inherited from the bcc Nb. The crystal-like and bcc-like medium range order clusters may be the structural origin for lower crystallization temperature in the as-rolled glass. It is demonstrated that hybrid reverse Monte Carlo simulations incorporating fluctuation microscopy and an empirical interatomic potential are insensitive to the starting structure.