Phase equilibria of low-Ni side in Nb-Ni-Ti system at 1100 °C

The phase equilibria related to liquid phase in low-Ni side of Nb-Ni-Ti system at 1100 degrees C were investigated through scanning electron microscope (SEM), electron probe micro-analyzer (EPMA), X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The results show that there exists liquid phase in equilibrium with continuous solid solution (Nb, beta Ti) and compound TiNi in low-Ni side of Nb-Ni-Ti system at 1100 degrees C. The liquid phase region originates from low-Ni side of binary Ti-Ni system and extends to 9.4 at% Nb in isothermal section of Nb-Ni-Ti phase diagram. The solid solubility of Nb in binary compound TiNi is about 10.6 at%. At 1100 degrees C, there exist two three-phase regions consisting of liquid+(Nb, beta Ti)+TiNi and (Nb, beta Ti)+TiNi+X(B)in Nb-Ni-Ti system, where X(B)is the compound with hexagonal structure and composition of 32.8Nb-44.5Ni-22.7Ti. The wide two-phase region (Nb, beta Ti)+TiNi exists between these two three-phase regions. In this two-phase region, Ti content in continuous solid solution (Nb, beta Ti) varies from 6.6 at% to 25.7 at%, but Ni content is almost the same, which is about 4.0 at%. The eutectic transformation L <->(Nb, beta Ti)+TiNi takes place at about 1138 degrees C in Nb-Ni-Ti ternary system.