Effect of Atomic Size and Valence Electron Concentration on the Formation of fcc or bcc Solid Solid Solutions in High Entropy Alloys

TL;DR

This study uses computational analysis to predict how atomic size and valence electron concentration influence the formation and structure of solid solutions in high entropy alloys with varying element counts.

Contribution

It provides a large-scale computational prediction of solid solution formation and structure in HEAs based on atomic size and VEC, expanding understanding of alloy design.

Findings

Solid solution formation decreases as the number of elements increases.

fcc and bcc structures are predicted based on VEC ranges.

The structure type correlates with the constant element's VEC value.

Abstract

The possibility of solid solution formation in high entropy alloys (HEAs) has been calculated for alloys with four to seven elements, using a rule previously reported. Thirty elements were included: transition elements of the fourth, fifth and sixth periods of the periodic table, and aluminum. A total of 2,799,486 systems were analyzed. The percentage of solid solutions that would be formed in HEAs decreases from 35.9% to 26.4%, as the number of elements increases from four to seven. The structure of the solid solutions, fcc, bcc or a mixture of fcc and bcc, that would be formed, has been predicted using a previously reported observation. The percentage of systems with fcc or bcc structure decreases as the number of elements increases from four to seven. The percentages of solid solutions with fcc, bcc or a mixture of fcc and bcc were calculated, for alloys with four to seven elements, but maintaining one constant element. Systems in which the constant element has valence electron concentration, VEC, from three to four, would have bcc structure in around 50% of the systems. Systems in which the constant element has VEC from ten to twelve, around 75% of systems would present fcc structure.