Effect of TiC addition on mechanical properties of dual two-phase Ni3Al-Ni3V intermetallic alloy

Dual two-phase intermetallic alloy that has an alloy composition of Ni75Al9V13Nb3 and is composed of geometrically close packed (GCP) Ni3Al (L12) and Ni3V (D022) phases was studied, focusing on the effect of TiC addition on high-temperature tensile properties. The two-phase microstructures defined by primary Ni3Al precipitates and eutectoid region consisting of Ni3Al and Ni3V phases were kept and were dispersed by TiC particles. EPMA analysis showed that alloy compositions in matrix of the TiC added alloy were different from those in the base alloy. The positive temperature dependence of flow strength was observed for all TiC added alloys. In low temperature range the maximum strengthening took place at 1 at.% TiC content. On the other hand, tensile elongation increased with increasing TiC content up to 1 at.% TiC content and was independent of TiC content over 1 at.% in whole temperature ranges. Also, the TiC addition resulted in change of the fracture mode from brittle transgranular fracture to ductile transgranular fracture in low temperature range, and from brittle intergranular fracture to ductile transgranular fracture in high-temperature range. Possible mechanisms responsible for the strengthening and ductilization by TiC addition were interpreted, based on the behavior of C and Ti solutes, and Nb solute in the matrix, which were decomposed from TiC and affected by TiC addition, respectively.