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

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 states, and equilibrium lattice parameters of these alloys are reported. The results show that quasi-chemical approach and vegard rule can satisfactorily predict the energetic and structural properties of FeCu alloys but fail to accurately 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 results show that the energetic and structural properties of these alloys can explain the element distribution of the Cu-rich precipitates in ferrite steels.