Atomic configuration and properties of austenitic steels at finite temperature: The effect of longitudinal spin fluctuations

TL;DR

This study investigates how longitudinal spin fluctuations influence the atomic configurations and properties of austenitic steels at finite temperatures, revealing significant effects on bonding, interactions, and short-range order.

Contribution

It introduces a model incorporating longitudinal spin fluctuations into thermodynamic simulations, showing their substantial impact on alloy properties and atomic ordering in austenitic steels.

Findings

LSF significantly alters bonding and interatomic interactions.

Calculated short-range order matches experimental data.

Ordering tendencies are similar across different alloy compositions.

Abstract

High temperature atomic configurations of fcc Fe-Cr-Ni alloys with alloy composition close to austenitic steel are studied in statistical thermodynamic simulations with effective interactions obtained in ab initio calculations. The latter are done taking longitudinal spin fluctuations (LSF) into consideration within a quasiclassical phenomenological model. It is demonstrated that magnetic state affects greatly the alloy properties and in particular, it is shown that the LSF substantially modify the bonding and interatomic interactions of fcc Fe-Cr-Ni alloys even at ambient conditions. The calculated atomic short-range order (SRO) is in reasonable agreement with existing experimental data for Fe0.56}Cr0.21Ni0.23, which has strong preference for the (001) type ordering between Ni and Cr atoms. A similar ordering tendency is found for the Fe0.75Cr0.17Ni0.08 alloy composition, which approximately corresponds to the widely used 304 and 316 austenitic steel grades.