Microstructure And Mechanical Properties Of Spark Plasma Sintering Ti-24Nb-4Zr-8Sn Alloys

Titanium and titanium alloy has a low density, high strength-modulus ratio, excellent wear resistance to corrosion and good biocompatibility, as human implant material has been widely used. But the most widely used clinically pure titanium and Ti-6A1-4V alloy and its application is limited due to its high modulus of elasticity, and Al, V biological toxicity.At present, the overall performance is more excellent Ti-Nb-Zr-Sn alloy has been widespread concern and attention, but it did not become the mainstream of clinical medicine. The reason is because the alloy Nb, Zr and other high melting point alloying elements, the density of these elements, the plastic is relatively poor, processing difficulties deformation, which put forward higher requirements for the alloy preparation techniques, and increased preparation costs. At present, for the preparation of containing refractory alloy elements titanium alloy vacuum consumable arc melting method. Prepared using this method alloy will inevitably composition segregation, organizational uneven or loose, shrinkage and other defects, this will lead to the mechanical properties and wear and corrosion performance of less than using the standard.This thesis Ti-24Nb-4Zr-8Sn(TNZS) alloy was prepared by spark plasma sintering technology, sintering temperature, heat treatment process, sintering of powder size on TNZS alloy density, microstructure and mechanical performance, the following conclusions:(1) Spark plasma sintering TNZS alloy has a higher density. Density with increasing sintering temperature in the sintering temperature range within the alloy: under the same sintering temperature, the use of a small particle size of the powders of the alloy having a higher density. The SPS approach reduces the sintering temperature of the alloy, to shorten the sintering time.(2)Discharge such as ion sintering method of preparation of the TNZS alloy organization formed by a large number of such as shaft-like β-Ti phase and Ti-Nb solid solution body of the mixing matrix and a small amount of needle-like and flaky a-Ti phase composition; with the sintering temperature, the alloy in the a-Ti opposing β-Ti phase change gradually, while the content of Ti-Nb alloy solid solution fewer and reduced in size, and tended to increase the compressive strength of the alloy.(3) Discharge such as ion sintering method preparation of TNZS alloy β-Ti phase content increased with decreasing particle size of powders; crystalline alloy is also more ideal, fine powder alloy Ti-Nb solid solution body of the number and size much smaller than the coarse powder alloy. The sintering temperature for the alloy elastic modulus smaller, the macrograined powder sintered alloy elastic modulus within the range of57-61GPa, powder sintering alloy elastic modulus within the range of40-48GPa. The fine powder sintered alloy elastic modulus is larger than the decrease macrograined powder, mainly to reduce the powder size, powder diffusion during the sintering process more fully, and therefore more uniform distribution of the alloy composition, the better continuity of the alloy matrix.(4) Alloy after solution treatment, the quantity of Ti-Nb solid solution are significantly reduced, which is due to the further diffusion of the alloying elements in solid solution treatment process, as well as some small grains gradually grow. After solution treatment the α-Ti phase content increased slightly, because of the greater degree of solid solution of β stabilizing element α"-Ti phase generated in the solution process. General aging treatment makes α" the opposite α ’phase transition. Solid solution alloys and sintered alloys compressive strength compared to some decline, mainly because of the larger grain size after solution treatment and alloy plastic improve. Meals solid solution alloys compression elastic modulus with elevated compared to sintered state, and the fine powder sintered alloy contrast trend.(5) After the aging treatment, α-Ti phase content is greatly improved, which is mainly in the solution process, a new generation of excessive phase α"-Ti phase transition α’-Ti phase, and phase decomposition of metastable β’-Ti α-Ti phase and β-Ti phase. MEALS sintered alloy after the aging treatment, the compressive strength and the elastic modulus declined sharply.