Abstract

This work summarizes the basics of phase diagrams and their relation to the Calphad method. It is emphasized that the benefits of quantitative prediction of phase formation of selected multicomponent alloys under equilibrium and special off-equilibrium processing conditions require the development of reliable and consistent thermodynamic descriptions forming a Calphad-type thermodynamic database. The implications of intermetallic phases in multicomponent Mg alloys are explained for ternary Mg-Ce-La/Nd alloys. An introduction to applications of this approach to phase formation in as-cast and heat treated Mg alloys is given and discussed in detail for the example of ternary Mg-Al-Zn alloys. The extension to truly multicomponent alloy systems and advanced kinetic calculations is briefly depicted.

Highlights

  • This work summarizes the basics of phase diagrams and their relation to the Calphad method

  • Materials, and (ii) the additional benefits of quantitative prediction of phase formation of a selected multicomponent alloy under equilibrium and special off-equilibrium processing conditions

  • The approximate prediction of phase formation in heat treated and as-cast alloys using equilibrium and Scheil simulation is currently one work horse of Integrated Computational Materials Engineering (ICME) because “only” the thermodynamic Calphad-type database is required but no kinetic data whatsoever. Such kinetic data are generally scarce, hindering more advanced calculations. This field is rapidly evolving, though; advanced kinetic calculations are consistently build upon proper knowledge of the thermodynamic descriptions

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Summary

PHASE DIAGRAMS AND THE CALPHAD METHOD

Phase diagrams are a cornerstone of knowledge in materials science and engineering. They are the perfect road map and starting point for designing all sorts of materials, such as alloys, ceramics, semiconductors, cement, concrete, or any material where the concept of phase is viable. Materials, and (ii) the additional benefits of quantitative prediction of phase formation of a selected multicomponent alloy under equilibrium and special off-equilibrium processing conditions Many of such applications are exemplified in a recent work [3], which is a primer on “How to Read and Apply Phase Diagrams” in the current environment of powerful software packages. The key point, the application of “Calphad-generated” databases in Materials Science & Engineering, is unique in the sense that it allows to proceed to truly multiphase and multicomponent phase equilibria This goes beyond calculation of phase diagrams. It encompasses the internally consistent calculation of any thermodynamic property and phase diagrams with the ability to extrapolate into unknown regions in temperature/composition space and into multicomponent systems. For magnesium alloys this approach has been demonstrated as a powerful tool in focused alloy design and process optimization [9,10,11]

MULTICOMPONENT THERMODYNAMIC
APPLICATIONS TO AS-CAST AND HEAT TREATED ALLOYS
Findings
CONCLUSIONS
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