Solid solution strain simulations compared with a topological model for glass formation in metallic alloys

Abstract

Recently a new criterion to predict the glass forming ability (GFA) of alloys has been introduced (M. F. de Oliveira, J. Appl. Phys. 111, 023509, 2012). The criterion is based on the topological instability of crystalline phases and electronic parameters (related to the mixing enthalpy). However the topological instability is derived from the approach introduced by Egami and Waseda ( T. Egami e Y. Waseda, J. Non-Cryst. Solids, 64, 113, 1984) with many approximations in its original form and also present in the final proposed approach. For example, the model was initially developed for substitutional solid solutions in single metals and now the same model is used for any kind of solid solution even for intermetallic phases. The topological instability is assumed to be linear with the amount of solute introduced in the matrix, which is probably true only for low concentrations. Therefore some questions arise and such questions could be, partially or fully, answered by using molecular dynamics. The model to be used is the embedded-atom method (EAM), in order to predict the strains in a solid solution matrix, which in turn are related to the topological instability. The main questions to investigate are: i. Are the solid solution strains linear with concentration? ii. Is the behavior of strains similar for both, single metallic phase or intermetallic? iii. Is the topological instability equation working properly for both cases? iv. Does it work for subtitutional and interstitial solid solution? v. The simulated topologial instability (strains) reaches local maxima for chemical compositions in good agreement with those predicted by the topological instability model? In order to answer such questions the EAM molecular dynamics of Zr-Cu and Zr-Cu-Al phases will be performed in a Blue Gene supercomputer from IBM at Rice University. This machine is shared with USP and can be acessed remotely, according to a collaborative term of research (signed in april 2012). (AU)