Microstructures and mechanical behaviors of NiAlFe intermetallic compounds

A series of Ni25Al-xFe (x = 20-40 at.%) intermetallic compounds were prepared for mechanical property measurements by means of hardness and tensile testing. The microstructural evolution of these alloys was examined by X-ray diffraction, high temperature differential calorimetry, optical microscopy, scanning electron microscopy and transmission electron microscopy. The results reveal that two phases, γ′ and β′, exist in the alloys with low iron content, and the microstructure changes from the mixture of γ′ and β′ phases to a nearly single β′ phase when the iron content reaches 40 at.%. An increasing iron content, which substitutes for nickel in this alloy, results in an increased melting point, hardness, yield stress and ultimate stress, but a decreased elongation.