Use of third generation data for the elements to model the thermodynamics of binary alloy systems: Part 1 – The critical assessment of data for the Al-Zn system. (March 2020)

• Record Type: Journal Article
• Authors: Dinsdale, Alan; Zobac, Ondrej; Kroupa, Ales; Khvan, Alexandra
• Is Part Of: Calphad. Volume 68(2020)
• Publication Date: 2020-03
• Subjects: CALPHAD assessment -- Al-Zn system -- 3rd generation unary data -- Concentration dependence of the Einstein temperature; Phase diagrams -- Data processing -- Periodicals; Thermochemistry -- Data processing -- Periodicals; Diagrammes de phases -- Informatique -- Périodiques; Thermochimie -- Informatique -- Périodiques; Thermodynamica; Electronic journals; 541.363
• DOI: 10.1016/j.calphad.2019.101723
• Languages: English
• ISSNs: 0364-5916

Abstract

Abstract: Over the last four years there has been a renewed interest in the development of new critically assessed data using physically based models. Nearly all work so far has been concerned with the critical assessment of data for the elements. This has involved the selection of Einstein or Debye temperatures for the stable crystalline phases and the liquid phase and associated parameters. However, until now, these data have not been extended in a comprehensive way to model the thermodynamic properties of binary, ternary and multicomponent systems. In this paper the way in which the parameters underlying these physical models vary with composition is explored. This includes a method to define the Einstein temperature for metastable phases of the elements and its relation to the so-called lattice stabilities used in the past, and the variation of the Einstein temperature with composition to account for the composition dependence of the excess entropy. This approach is demonstrated for the Al-Zn system which shows extensive regions of solid solution and complete miscibility in the liquid phase. Here Einstein temperatures are derived for Al in the HCP_ZN phase and Zn in the FCC_A1 phase together with parameters describing the variation of the Einstein temperature with composition for the HCP_ZN, FCC_A1 and liquid phases. Highlights: The composition dependence of data for the solution phases were described using 3rd generation models. A simple entropy difference between two crystalline phases can be expressed in terms of a ratio of 2 Einstein temperatures. The composition dependence of excess entropy of mixingmay be transformed into a variation of the Einstein temperature. Data for the Al-Zn system were critically evaluated. An almost exact correspondence was found with what we considered to be, the most reliable published assessment. Future work will explore systems where the component elements have significantly different melting points.