Development of NiAl-based intermetallic alloys: effect of chromium addition

The mechanical behavior of dual-phase NiAl(Cr) microstructures, consisting of elongated primary NiAl grains aligned with an intergranular NiAl-Cr eutectic phase, produced by extrusion of a cast NiAl(Cr) alloy, has been examined. Chromium addition to create a dual phase NiAl-based aligned microstructure leads to large increases in the yield strength but no significant toughness improvement. This is achieved primarily by solid solution hardening and precipitation hardening. The constitutional hardening rate resulting from deviations from stoichiometry in the nickel-rich NiAl was estimated to be about 66 MPa per atomic per cent of nickel.