A novel approach was used to characterize B2-ordered (Ni,Fe)Al single-phase fields over wide ranges of composition and temperature. This approach involved atom location via the channeling-enhanced micro-analysis determination of atomic site occupancies and vacancy concentrations. The triple-defect structure was observed over the entire phase field. Qualitative thermodynamic predictions, that the Fe antisite was more stable than the Ni antisite, were confirmed. However, in some parts of the phase field it was found that Ni antisite concentrations were higher than expected on the basis of simplistic thermodynamic predictions of site preference. It was concluded that the solute atoms did not directly harden the material, but affected the hardness by altering the concentrations of other point defects.

Site Occupancies, Point Defect Concentrations and Solid Solution Hardening in B2 (Ni,Fe)Al. L.M.Pike, I.M.Anderson, C.T.Liu, Y.A.Chang: Acta Materialia, 2002, 50[15], 3859-79