Experimental investigation and thermodynamic calculation of the Al–Mg–Zn system

Phase equilibria and transformations in ternary Mg-rich Mg–Y–Zn alloys

BINGSS is a program for least squares optimization of thermodynamic descriptions using experimental phase diagram and thermodynamic data. The number of measured values used is unlimited. Some special features and improvements since the first publication of this program are outlined. The models for the thermodynamic description and their adjustable coefficients must be well selected. Missing parameters may disable the fit between experimental and calculated values. Too many coefficients may be undefined and may cause divergence of the calculation. Some ideas on how to handle these problems are demonstrated using the Mg-Zn system as an example.

Demonstration of the use of “BINGSS” with the Mg-Zn system as example

Magnesium-based alloys are becoming a major industrial material for structural applications because of their potential weight saving characteristics. All the commercial Mg alloys like AZ, AM, AE, EZ, ZK, and so forth series are multicomponent and hence it is important to understand the phase relations of the alloying elements with Mg. In this work, eleven essential Mg-based binary systems including Mg-Al/Zn/Mn/Ca/Sr/Y/Ni/Ce/Nd/Cu/Sn have been reviewed. Each of these systems has been discussed critically on the aspects of phase diagram and thermodynamic properties. All the available experimental data has been summarized and critically assessed to provide detailed understanding of the systems. The phase diagrams are calculated based on the most up-to-date optimized parameters. The thermodynamic model parameters for all the systems except Mg-Nd have been summarized in tables. The crystallographic information of the intermetallic compounds of different binary systems is provided. Also, the heat of formation of the intermetallic compounds obtained from experimental, first principle calculations and CALPHAD optimizations are provided. In addition, reoptimization of the Mg-Y system has been done in this work since new experimental data showed wider solubility of the intermetallic compounds.

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Essential Magnesium Alloys Binary Phase Diagrams and Their Thermochemical Data

a b s t r a c t All available thermodynamic and phase diagram data of Mg–Zn, Mg–Sn and Sn–Zn are critically evaluated and most reliable data are incorporated to model each system. The binary liquid phases are modeled using the modified quasi-chemical model in order to incorporate the strong ordering in the Mg–Sn and Mg–Zn systems. The binaries are extrapolated to construct the Mg–Sn–Zn ternary using the symmetric Kohler geometric model without using any ternary interaction parameter. The calculated Mg–Sn–Zn ternary diagram shows very good consistency with the published experimental data.

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E. Sommer

Papers

Assessment of the Mg-Zn System