Glass formation in binary alloy systems: A prediction of the composition range

Abstract

A semi-empirical theory is used to calculate the composition range of binary amorphous alloys. The theory is based on the comparison of the free energies of the amorphous alloy and competing crystalline phases: terminal solid solutions and intermetallic compounds with simple structures. The enthalpy of formation of the solid solution is expressed as a sum of two contributions: a chemical contribution arising from electronic redistribution in forming the alloy, and an elastic contribution arising from the difference in size between solute and solvent atoms. The enthalpy of formation of the amorphous phase has only the chemical contribution. The theory clearly shows the key role that atomic size mismatch plays in determining the glass-forming concentration range, which is successfully computed for an illustrative sample of binary alloy systems. A connection of our treatment with the work of other authors is also provided.