The energetic and structural properties of bcc NiCu, FeCu alloys: a first-principles study

TL;DR

This study uses first-principles calculations to analyze the energetic and structural properties of bcc NiCu and FeCu alloys, revealing differences in predictability and magnetic effects relevant to steel precipitates.

Contribution

It provides the first-principles analysis of bcc NiCu and FeCu alloys, highlighting the limitations of quasi-chemical and Vegard rule predictions for NiCu due to magnetic interactions.

Findings

Vegard rule predicts FeCu properties well but not NiCu.

Magnetic state differences influence bond energy variations.

Results explain local composition of precipitates in ferrite steels.

Abstract

Using special quasirandom structures (SQS's), we perform first-principles calculations studying the metastable bcc NiCu and FeCu alloys which occur in Fe-Cu-Ni alloy steels as precipitated second phase. The mixing enthalpies, density of state, and equilibrium lattice parameters of these alloys are reported. The results show that quasi-chemical approach and vegard rule can well predict the energetic and structural properties of FeCu alloys but fail to yield that of NiCu. The reason rests with the difference of bond energy variation with composition between NiCu and FeCu alloys induced by competition between ferromagnetic and paramagnetic state. Furthermore, the calculated results show that the energetic and structural properties of these alloys can well explain the local composition of the corresponding precipitates in ferrite steels.