Microstructural factors affecting hardness property of dual two-phase intermetallic alloys based on Ni3Al–Ni3V pseudo-binary alloy system

Abstract Dual two-phase intermetallic alloys that have alloy compositions of Ni 75 Al x Nb 2.5 V 22.5− x and are composed of geometrically close packed (GCP) Ni 3 Al (L1 2 ) and Ni 3 V (D0 22 ) phases containing Nb were studied, focusing on the relationship between microstructural parameter and high-temperature hardness property. The two-phase microstructures defined by primary Ni 3 Al precipitates and eutectoid (i.e., channel) region (consisting of Ni 3 Al and Ni 3 V phases) were characterized in terms of size, volume fraction and number density of primary Ni 3 Al precipitates. The high-temperature hardness was evaluated as a function of temperature. The volume fraction of primary Ni 3 Al phase precipitates, and interfacial area between primary Ni 3 Al precipitates and channel region were found to be important factors affecting the hardness of the dual two-phase intermetallic alloys. Possible mechanisms responsible for the observed extra hardening were discussed, taking the role of interfaces among the constituent phases into consideration.