Isothermal sections of the Co-Ni-Ti system at 950 and 1000 °C

The isothermal sections of the Co-Ni-Ti system at 950 and 1000 degrees C were investigated experimentally. Diffusion couples were measured by electron probe microanalysis to construct the phase relations at 950 degrees C, whereas eleven key alloys annealed at 1000 degrees C were investigated using X-ray diffraction and electron probe microanalysis. The ternary phase, tau-(Co, Ni)(3)Ti (hP24-VCo3), was observed at both temperatures. At 950 degrees C, continuous solid solutions are formed between CoTi2 and NiTi2 as well as between CoTi and NiTi. Eight 3-phase regions, i.e. Ni3Ti + (Co, Ni) Ti + tau, Ni3Ti + gamma-(Co, Ni) + tau, tau + c-Co2Ti + (Co, Ni)Ti, tau + c-Co2Ti + Co3Ti, tau + Co3Ti + gamma-(Co, Ni), c-Co2Ti + h-Co2Ti + Co3Ti, L + beta-(Ti) + (Co, Ni)Ti-2 and L + (Co, Ni)Ti-2 + (Co, Ni) Ti, were constructed at 1000 degrees C. Considerable ternary solubilities in Ni3Ti, Co3Ti and c-Co2Ti were determined.