The phase equilibria related to liquid phase in low-Ni side of Nb-Ni-Ti system at 1100℃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,βTi)and compound TiNi in low-Ni side of Nb-Ni-Ti system at 1100℃.The liquid phase region originates from low-Ni side of binary TiNi 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℃,there exist two three-phase regions consisting of liquid+(Nb,βTi)+TiNi and(Nb,βTi)+TiNi+X_B in Nb-Ni-Ti system,where X_B is the compound with hexagonal structure and composition of 32.8 Nb-44.5 Ni-22.7 Ti.The wide two-phase region(Nb,βTi)+TiNi exists between these two three-phase regions.In this two-phase region,Ti content in continuous solid solution(Nb,βTi)varies from6.6 at%to 25.7 at%,but Ni content is almost the same,which is about 4.0 at%.The eutectic transformation L■(Nb,βTi)+TiNi takes place at about 1138℃in Nb-Ni-Ti ternary system.
