| Titanium and titanium alloy has non-toxic, no magnetic, good corrosion resistance, low elastic modulus, light weight and excellent biocompatibility,etc. in aerospace, especially medicine area has huge market potential, the conventional titanium and titanium alloys forming methods have moulded forming, injection molding, isostatic pressing, explosive forming, etc. the base was produced by the method often needs further treatment such as scraps, not only reduce the working efficiency and increased the cost of production, near-net forming technology can be used to solve the problem, it almost no need to pass the subsequent processing, has the short process step, good product quality and production cost is low, therefore, this kind of powder metallurgical technology is worth developing and promotion. Based on this cognition, the topic research purpose lies in making pure Ti and Ti-6A1-4V alloy products that accord with biomedical standards by near-net forming technology; Through the analysis of the test will obtain the best process parameters for near-net forming technology of TiH2and Ti-6A1-4V alloyand analyze the reason that has caused appear to crack for base of near-net forming.The traditional powder metallurgy method usually adopt the sinter titanium and titanium alloy powder production titanium products, this experiment to adopt new near-net forming technology to preparation pure Ti and Ti-6Al-4V alloy,with the powder of TiHb and Al-V alloy elements as raw material and adopting the blended elemental powder (BE), pressure forming, completing this process of hydrogenated titanium dehydrogenation and powder sintering at the same time, can be directly made the titanium alloy products thatthe density close to100%by this process, not only reduces the process step and the cost of production, but also its performance also is close to or exceeded forging and machining product performance, laying a solid foundation for the next step of the industrialization of the production.The experiment has researched these parameters that include themix powder, pressing, sintering and dehydrogenation, etc,on the influence on the performance of the product and further analyzedthe change rule of pore morphologies, microstructure, fracture morphology of the sintering base under different sintering temperature and pressure, sintering temperature, holding time to the influence of mechanics properties of sintering base, determinedthe suitable processing parameters fornear-net forming technology of TiH2and Ti-6Al-4V alloy. Through the forming experiment concluded that:(1) large grain size powders than low particle size of the powders easier to shape,the forming process to determine the suitable parameters for:pressure for360MPa, boost rate for4MPa/S, step-down rate for2MPa/S, the holding time for150S.(2)through to the Ti-H system state diagramand TG-DSC curve analysis, and with the test of temperature, time to the influence of dehydrogenation rate, concludes that when the temperature for950℃of dehydrogenation, holding time for4hours, hydrogen can be completely removal basic.(3) according to the sintering temperature, heating rate and holding time on the relationship for the density curve obtain thesuitable sintering temperature is1200℃, holding time for4hours.(4) drawing theradial density distribution rule for the base of near-net forming technology is:edge density is higher than the density of center, from outside to inside the density have been gradually declined; Axial density distribution rule is:the central density is higher than the density of the bottom and top.(5) the main factors to crack for base of thenear-net forming for:powder features diversification, internal gas of base was not completely removed demoulding, inappropriate use additives and elastic after-effect. |
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