Ductility and magnetism: An ab-initio study of NiAl–Fe and NiAl–Mn alloys

An ab-initio density functional approach is applied to study the magnetism related aspects of ductility for NiAl microalloyed by Fe and Mn. The generalised stacking fault energies of NiAl are calculated for slip interfaces in which some of Ni and Al atoms are replaced by Fe(Mn) atoms. By comparing spin-polarised and nonmagnetic calculation, it is shown that the local magnetic moment of Fe atom impedes a change of the preferred slip system from 〈001〉 to 〈111〉. The opposite effect is found for NiAl–Mn, in which 〈001〉 slip is significantly unfavored. The results are in general in excellent agreement with experimental observations, verifying improved ductility for NiAl–Fe. The differences in slip behavior are correlated with the changes of the local magnetic moments in 〈001〉 and 〈111〉 slipped NiAl.