Magnetism-induced solid solution softening in NiAl with Co, Fe, Mn, and Cr solute atoms: theory and experiment

By taking the solid solution effect of Co, Fe, Mn, and Cr solutes in Ni-rich NiAl as an example, we have determined, through a combination of alloying behavior experiments, first-principles calculations, and neutron diffraction measurements, that magnetism has a profound impact on the mechanical properties of intermetallics. Co solutes do not affect the hardening behavior of NiAl alloys. Fe solutes, on the other hand, induce the most substantial and unusual solid solution softening among these solutes. These results can only be explained by the presence of magnetic interactions induced by solutes located on the Al sublattice. The predicted magnetic moment of Fe solutes was verified by neutron diffraction experiment. Our investigation points out the inadequacy of the conventionally used Goldschmidt radii in addressing the atomic size effect in intermetallics.