Dresden 2020 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 51: Computational Materials Modelling - Mechanical Properties

MM 51.1: Talk

Thursday, March 19, 2020, 10:15–10:30, IFW B

Atomic scale investigation of internal friction in austenitic steels — •Osamu Waseda, Tilmann Hickel, and Jörg Neugebauer — MPIE Düsseldorf

Internal friction measurements are a powerful method for the identification of the nature of point defects and complex short range order of solute atoms in austenitic steels. Whereas it is possible to identify point defect interactions that contribute to internal friction, it is difficult to decompose experimental results into each cause, as the complex interactions and the stochastic nature of solute diffusion smear out different contributions. Therefore, the interpretation of experimental results requires assumptions that are currently a matter of discussion. Correspondingly, a theoretical model that yields quantitative agreement with experiments is still missing for austenite. In this study, we developed a novel thermodynamic method conjugated with ab initio calculations to understand the short range ordering generated by vacancies and carbon atoms. This model not only accounts for the variation of solute interactions due to material deformation, but also the variation of migration energies due to solute interactions. In this way, it removes the commonly known discrepancy between empirical models and experimental results. This model, therefore, enables us to decompose experimental internal friction results into each contribution of point defect interactions. This clarifies the nature of short range order of carbon and vacancies in austenite, which is decisive for their mechanical performance.