Microstructure, mechanical properties and wear of Ni–Al–Fe alloys

The purpose of this paper is to describe the microstructure, mechanical properties and wear behavior of NiAl-based alloys both with and without a ductile b.c.c. phase. The materials studied had equiatomic amounts of Ni and Al, with four different additions of iron – 10, 20, 30 and 44 at.%. The microstructures were examined using both optical microscopy and transmission electron microscopy. The alloys containing 10 and 20% iron were single phase with an ordered b.c.c. (or B2 structure), whilst those containing 30 and 44% Fe were two-phase with a B2 matrix containing fine b.c.c. precipitates. The addition of iron did not improve the room temperature tensile ductility significantly, although some increase in both the compressive yield strength and the hardness was noted as the iron content increased. Wear tests, which were conducted in an argon atmosphere to minimize environmental effects, showed a higher wear rate for the two-phase alloys despite their slightly higher hardnesses, presumably due to shear of the ductile phases present in these alloys.