Microstructural factors affecting hardness property of dual two-phase intermetallic alloys based on Ni 3Al–Ni 3V pseudo-binary alloy system

Abstract

Dual two-phase intermetallic alloys that have alloy compositions of Ni 75Al x Nb 2.5V 22.5− x and are composed of geometrically close packed (GCP) Ni 3Al (L1 2) and Ni 3V (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 3Al precipitates and eutectoid (i.e., channel) region (consisting of Ni 3Al and Ni 3V phases) were characterized in terms of size, volume fraction and number density of primary Ni 3Al precipitates. The high-temperature hardness was evaluated as a function of temperature. The volume fraction of primary Ni 3Al phase precipitates, and interfacial area between primary Ni 3Al 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.