Thermodynamic calculations and phase diagrams for magnesium and its alloys: Part II

Abstract

Magnesium is the lightest structural metallic material with a density of 1.741 g/ cm, in comparison with the densities of aluminum (2.70 g/cm) and iron (7.86 g/cm). This makes magnesium alloys particularly attractive for transportation applications for weight reduction and higher fuel effi ciency. World consumption of magnesium alloys in the auto industry has grown by 15% per year for more than a decade. To understand factors that infl uence the properties of magnesium alloys, the U.S. auto industry has called for research into the fundamentals of these alloys, including phase equilibrium and computational thermodynamics. Computational methods are powerful tools to understand materials behaviors and to support selection and design of materials. The core component in computational materials science is computational thermodynamics; the development of new materials and improvement of existing materials from scratch requires that they satisfy thermodynamic stability conditions. In addition, knowledge of the thermodynamics of a system can guide the selection of the kinetic paths the material processing must follow to achieve the desired structure and properties. In computational thermodynamics, known as the CALPHAD (CALculation of PHAse Diagram) method, the Gibbs energy of individual phases is modeled in terms of their crystal structures. The model parameters are evaluated with data from both phase equilibria and thermochemistry and collected in thermodynamic databases. Starting Thermodynamic Calculations and Phase Diagrams for Magnesium and Its Alloys: Part I