Research Of Ternary Compound X_B And Phase Equilibrium On Nb-Ni-Ti Ternary Phase Diagram

Nb-Ni-Ti ternary phase diagram study began in the1960s, High temperature alloys, superconducting alloys and shape memory alloy perfect the design and development of related materials.But the phase equilibrium of the existing research results mainly is in the solid state, and studies of ternary compound and its phase equilibrium there are larger differences, especially compound XB phase crystal structure and phase equilibrium of missing information. And the nascent hydrogen Nb base casting filter material of design urgently need the alloy, especially the high temperature phase equilibrium research support. XB phase and phase equilibrium data related to the lack of a direct impact on hydrogen filter membrane material composition design and preparation technology.This research uses the alloy balance organization structure analysis, the use of optical and scanning electron composition of microstructure analysis, energy spectrum analysis,X-ray diffraction (XRD) and transmission electron diffraction structure analysis, combined with the thermal analysis, XB phase composition,crystal structure and composition and phase equilibrium was studied, and obtain the following results:(1) The solubility of Nb-Ni-Ti-based binary compounds is high to the third group of elements.The solid solubility of binary compounds TiNi can be13.7at.%to the third group of element Nb at1000℃, and the solubility of Ni3Nb to Ti can be6.7at.%.(2) The compound XB which has a hexagonal crystal structure can keep the balance between(βTi,Nb),TiNi,XA,XD,Ni3Nb at temperature range of1000-1150℃(3) AT1000℃, the phase diagram of Nb-Ni-Ti-based isothermal section exists (βTi,Nb)+TiNi+XB,TiNi+XA+XB,XA+XB+XD andXB+XD+Ni3Nb,which are associated with the compound XB-phase. The XB-phase and binary compounds Ni6Nb7dissolve to one phase because of the increased increased solubility of solid solution;As we maintain the same hexagonal crystal structure, the lattice constant decreases while the content of Ti increases from a=b=0.435nm.and c=2.620nm to a=b=0.492nm x=2.664nm of Ni6Nb7continuously.(4) In the phase diagram of the Nb-Ni-Ti system1100℃isothermal section, the three-phase region (pTi,Nb)+TiNi+XB,TiNi+XA+XB,XA+XB+XD, exist all the time, but because of the emergence of liquid, XB+XD+Ni3Nb phase regions didn’t exist.(5) At1150℃, there are three-phase regions ((3Ti,Nb)+TiNi+liq and (βTi,Nb)+liq+XB. The composition range of liquid region are19.5-30.4at%Nb,8.4-34.4at%Ti.