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

Dual two-phase intermetallic alloys that have alloy compositions of Ni75AlxNb2.5V22.5-x and are composed of geometrically close packed (GCP) Ni3Al (L1(2)) and Ni3V (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 Ni3Al precipitates and eutectoid (i.e., channel) region (consisting of Ni3Al and Ni3V Phases) were characterized in terms of size, volume fraction and number density of primary Ni3Al precipitates. The high-temperature hardness was evaluated as a function of temperature. The volume fraction of primary Ni3Al phase precipitates, and interfacial area between primary Ni3Al 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. (C) 2009 Elsevier Ltd. All rights reserved.