At present, the development of titanium alloys in biomedical materials is mainly dominated by titanium-niobium, titanium-molybdenum and titanium-tantalum alloy systems. Titanium-15 tantalum-15 niobium casting alloy has tensile strength of 102ksi, yielding strength of 72ksi, elongation of 12%, Young's coefficient of 80GPa, compared with common commercial biomedical materials G4 and 64Ti, has great development potential. In this paper, the microstructure of titanium-15 tantalum-15 niobium alloy casting is analyzed, which is the basis for the application and processing of biomedical materials. The main research results are as follows: 1. In the casting state, the microstructure of titanium-15 tantalum-15 niobium alloy is a mixture of five phases, including: hexagonal closest packing (HCP) structure αa, αb phase, body-centered cubic (BCC) structure β phase, hexagonal structure ω phase and body-centered cubic (BCT) structure H phase. 2. According to the ratio of I0001/I0002, αa is the lower phase of alloying elements, αb is the mixed phase of high alloying elements; Two phases along the 0001 axis, the gap of 1~2°, this phenomenon has not been proposed by scholars. The existence of β and ω phase is consistent with the general observation of scholars. In addition, the H phase structure is a newly discovered phase. According to TEM diffraction pattern analysis, H(Hui) phase is a body-centered tetragonal (BCT) structure with lattice constants a=b=0.328nm, c=0.365nm, c/a≒1.11. 3. Mixed phase of alloy casting state.
The effects of microstructure, phase composition and surface morphology on resistivity, temperature coefficient and electrochemical properties of titanium nitride, tantalum nitride nano films and titanium-tantalum nitride ternary composite films with both properties were discussed by changing the process parameters of nitrogen flow rate and target material. Thin film deposition is performed by controlling the target material and feeding different nitrogen flow ratios. The microstructure and crystalline phase of these films were analyzed by low-sweep X-ray diffractometer, the surface morphology was observed by scanning electron microscope, and the resistivity and temperature coefficient of the films were measured by four-point probe, surface roughness meter and heating platform. Finally, the electrochemical properties of the films were analyzed by potentiostat and electrochemical AC impedance analyzer. The experimental results show that the deposition rate of the film will change with the change of process parameters, and the film thickness will decrease with the increase of nitrogen ratio. The microstructure and surface morphology of the films also change with the proportion of nitrogen.
