凝胶注模成形钛合金的研究

发布时间：2018-05-19 14:26

  本文选题：凝胶注模 + 钛合金　； 参考：《北京科技大学》2015年博士论文

【摘要】：钛合金具有密度低、比强度高、耐热性强、耐蚀性好等优异性能,被誉为“21世纪的金属”,是极具发展前景的结构材料。钛及其合金不仅在航空航天领域有着十分重要的应用,在化工、石油、轻工、冶金、医学、体育、民用等行业也有着广阔的应用前景。然而,由于钛的生产成本较高,大大限制了它的应用。因此,研发钛产品新制备工艺,对降低成本和扩大钛的应用范围意义重大。 粉末冶金技术能够满足钛合金低成本与高性能的双重目标。以开发大尺寸复杂形状钛合金结构件为目的,本课题提出利用凝胶注模成形制备钛合金。针对粉末钛合金的控氧难题,从三方面展开：在制粉方面,利化低氧氢化-脱氢工艺制备高纯低氧氢化钛及钛粉；在成形方面,开发无氧凝胶体系；在烧结方面,研究镁、钙、钕对致密化及氧的富集作用,结果如下： 利用氢化-脱氢工艺制备出100目、200目、325目、500目的氢化钛及钛粉产品。制粉过程中利用高纯氢控制氢化过程的增氧、氮气保护控制破碎过程的增氧、高真空控制脱氢过程的增氧；且工序转换时避免粉末与空气接触,获得氧含量1000ppm的氢化钛及钛粉。 对比了氢化钛及钛粉的凝胶注模成形性能,氢化钛及钛粉固含量分别为50vol.%、37vol.%；经1300°C烧结后,氢化钛烧结相对密度95.9%,收缩率为22.5%,钛粉烧结相对密度为92.5%,收缩率为20.8%,因而氢化钛更适宜作为凝胶注模成形的原料。 针对常用聚合物凝胶体系氧残留高的问题,开发无氧聚苯乙烯凝胶体系：1)在油酸含量0.55wt.%、苯乙烯含量50vol.%、固含量49vol.%的条件下,可得低粘度、高固含量的浆料；在二乙烯基苯含量40vol.%(苯乙烯含量10vol.%)、反应温度90℃、引发剂含量130mmol·L-1的条件下,固化时间约3.5h,坯体强度为20MPa；2)将低分子量有机凝胶成功引入到成形中,经球磨后浆料固含量达51vol.%；凝胶温度为40～45℃时,固化时间为3～10min；聚苯乙烯浓度为0.08g·mL-1的条件下,坯体强度为10MPa。 聚苯乙烯体系的增氧及增碳量分别为0.07wt.%、0.2wt.%,低分子量有机凝胶体系的增氧及增碳量分别为0.1wt.%、0.16wt.%,利用该无氧体系成形出纯钛的抗拉强度510MPa、延伸率6.5%； 研究了镁、钙、钕对氢化钛粉末烧结致密化及氧的影响,镁、氢化钙、钕均能促进氢化钛粉末的烧结致密化,在0.5wt.%Mg、0.375wt.%CaH2、0.5wt.%Nd的条件下,分别将烧结相对密度由96%提高到98.1%、98.2%、98.6%。由于密度的提高,添加镁的样品抗拉强度为538MPa、延伸率7.1%,得益于密度提高及氧的富集,Ti-0.375Ca样品的抗拉强度为545MPa、延伸率9.2%, Ti-0.5Nd样品的抗拉强度为590MPa、延伸率10.1%。 利用凝胶注模成形开发出钛门把手产品,成本约73元/kg,与传统不锈钢、铜合金、锌铝合金等材质门把于相比,具有质轻、美观、生物相容性优异等特点,易于宣传推广,市场前景广阔,有望促进钛在民用领域的大范围应用。
[Abstract]:Titanium alloys with low density, high specific strength, strong heat resistance, good corrosion resistance and other excellent properties, known as "21 century metal", is a very promising structural materials. Titanium and its alloys not only have very important applications in the field of aerospace, but also have broad application prospects in chemical, petroleum, light industry, metallurgy, medicine, sports, civil and other industries. However, because of the high production cost of titanium, its application is greatly limited. Therefore, it is of great significance to develop a new preparation process for titanium products to reduce the cost and expand the application range of titanium. Powder metallurgy technology can meet the dual goals of low cost and high performance of titanium alloy. In order to develop large size and complex shape titanium alloy structural parts, this paper presents the preparation of titanium alloy by gel injection molding. Aiming at the problem of controlling oxygen in powder titanium alloy, the following three aspects are carried out: in the aspect of powder making, the preparation of high purity and low oxygen titanium hydride and titanium powder by using the technology of dehydrogenation and dehydrogenation of low oxygen, the development of anoxic gel system in forming, the study of magnesium and calcium in sintering, The effect of neodymium on densification and oxygen enrichment is as follows: Titanium hydride and titanium powder were prepared by hydrogenation-dehydrogenation process. High purity hydrogen is used to control the oxygenation in the hydrogenation process, nitrogen protection to control the oxygen increase in the breaking process, and high vacuum to control the oxygen increase in the dehydrogenation process, and to avoid the contact between the powder and the air during the process conversion, and to obtain titanium hydride and titanium oxide with oxygen content of 1000ppm. The gel injection molding properties of titanium hydride and titanium powder were compared. The solid content of titanium hydride and titanium powder were 50vol.37vol.0.After sintering at 1300 掳C, The relative density of titanium hydride sintering is 95.9, the shrinkage ratio is 22.5. the relative density of titanium powder sintering is 92.5 and the shrinkage rate is 20.8.The titanium hydride is more suitable as raw material for gel injection molding. Aiming at the problem of high oxygen residue in common polymer gel system, the low viscosity and high solid content slurry can be obtained under the conditions of oleic acid content 0.55 wt., styrene content 50 vol.and solid content 49vol.%. The low molecular weight organic gel was successfully introduced into the forming process under the conditions of the content of divinylbenzene (40 vol.% styrene, reaction temperature 90 鈩，

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