C06 – Thermodynamic Modelling of the Mg–Al–Ca System and its Defect Phases

PI: Dr. Bengt Hallstedt (Institute for Materials Applications in Mechanical Engineering, RWTH Aachen, Augustinerbach 4, 52062 Aachen)

SFB researchers: Mehdi Noori (Institute for Materials Applications in Mechanical Engineering, RWTH Aachen, Augustinerbach 4, 52062 Aachen) until August 2022

In this project, a new Calphad description for the Mg–Al–Ca system is being developed, which describes all important phases over the complete concentration and temperature ranges. New crystallographically based sublattice models are used to model the C14, C15 and C36 Laves phases as well as the γ-Mg₁₇Al₁₂ phase. This will be possible by completely basing the modelling on ab initio calculations of the energies of formation of all possible permutations of the crystal occupancies. Thermodynamic calculations are used to understand the microstructure formation in the alloys, in particular composite alloys investigated within the CRC. While knowledge about the phase diagram and the thermodynamic properties of its (bulk) phases is necessary for the development and processing of alloys, many of their properties are determined by defects, in particular grain boundaries, phase interfaces and dislocations. However, the thermodynamic properties of defects and their transitions between different states (or phases) are much less understood. A central theme within the CRC is the development of defect phase diagrams, i.e. the investigations of transitions between different defect states. In this project, thermodynamic models for different defect states will be developed, which can be used to calculate equilibria between different states in order to build defect phase diagrams.