Published online by Cambridge University Press: 03 March 2011
The refractory element Ta was added to L12-type Ni3(Si,Ti) intermetallic alloys in order to substitute for Ti. The microstructure and the mechanical properties of the alloys were investigated as a function of the Ta content. All the alloys were doped with 50 wt.ppm boron to suppress intergranular fracture. The alloys containing up to 5 at.% Ta showed an L12 single-phase microstructure, while the alloys containing more than 5 at.% Ta exhibited a two-phase microstructure consisting of Ni3Ta particles in the L12 matrix. At room-temperature (RT), the hardness of the alloys with the L12 single-phase microstructure increased with increasing Ta content due to solid solution hardening of Ta. RT yield stress (0.2% yield strength) and tensile ultimate strength of the alloys with the L12 single-phase microstructure increased with increasing Ta content keeping a high level of tensile elongation. At high-temperature (HT), the positive temperature dependence of hardness was observed in all the alloys, irrespective of Ta addition. HT hardness was also enhanced by the addition of Ta. It was consequently demonstrated that Ta is a remarkable solid solution hardening element in the Ni3(Si,Ti) alloys.