SKM 2023 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 22: Mechanical Properties and Alloy Design: Porous and Nanostructured Materials

MM 22.6: Vortrag

Dienstag, 28. März 2023, 15:30–15:45, SCH A 118

Phase stability of iron and its alloys from first principles dynamical simulations and thermodynamic integration — •Davide Gambino and Björn Alling — Linköping University, Linköping, Sweden

In recent years, thermodynamic integration (TI) based on first principles simulations has been shown to accurately reproduce phase diagrams and is now able to guide the design of functional materials and alloys. For what concerns iron and steels, this methodology is complicated by the presence of magnetic degrees of freedom (DOF) and their interplay with electronic and vibrational DOFs. Here I will show how the phase stability of iron and its alloys can be obtained from first principles employing atomistic spin dynamics - ab initio molecular dynamics (ASD-AIMD) simulations and TI accounting for all DOFs [1].

The free energy difference between bcc and fcc Fe was calculated close to the melting point in the magnetically disordered state, carrying out TI over stress-strain variables along the Bain path, and then propagating it to low temperatures with TI over temperature employing the ASD-AIMD energies. The method captures the α → γ → δ transitions, with the latter transition temperature reproduced within 50 K from experiments, and the calculated Gibbs free energy difference being within 5 meV/atom from the CALPHAD estimate over the whole temperature range. The method is then applied to Fe_1−xMn_x alloys for concentrations of x=0.05, 0.10 and for temperatures T ≥ 1400 K and results are compared with the experimental phase diagram.

[1] Gambino et al., arXiv:2210.14718 [cond-mat.mtrl-sci]