Use of third generation data for the elements to model the thermodynamics of binary alloy systems: Part 2 – The critical assessment of data for the Pb-Sn system

Abstract

It had been shown previously that the application of the new models for pure elements sometimes requires the use of two Einstein temperatures to describe the thermodynamic properties of the phases. In the present work we discuss methods to define the Einstein temperature for metastable phases of elements, in particular for the BCT_A5 phase, which has been described using multiple Einstein temperatures, and the variation of these Einstein temperatures with composition to account for the composition dependence of the excess entropy. This approach is demonstrated here for the Pb-Sn system which shows solid solution regions. Einstein temperatures were derived for BCT_A5 Pb, BCC_A2 Pb, BCC_A2 Sn FCC_A1 Sn, HCP_A3 Sn and HCP_A3 Pb phases together with parameters describing the variation of the Einstein temperatures with composition for the BCT_A5, FCC_A, HCP_A3, BCC_A2 and liquid phases.