Description of chemical ordering in amorphous alloys

Abstract

Partial coordination numbers Zij* for a chemically disordered binary amorphous alloy AXABXB are obtained in terms of total coordination numbers Zi and average coordination numbers 〈Z〉 Zij*=xjZiZj /〈Z〉. Departures from complete chemical disorder are characterized by a short-range order coefficient with ηABmax=xBZB/x AZA for XBZB<xAZA and ηABmax=xAZA/x BZB for xBZB>xAZA. For complete chemical disorder νAB0 = 0; for complete chemical order, i.e. with chemical preference for AB nearest neighbor pairs, νAB0 = 1. For departures from chemical disorder associated with clustering, i.e. chemical preference against AB nearest neighbor pairs, νAB0 < 0. Experimental results for several amorphous alloys are used to demonstrate the usefulness of these results. A more precise calculation of ηABmax is necessary to compare the degree of ordering in the metal-metalloid and metal-metal alloys. © 1981.