Weldability and microstructural variations in weldments of Ti-5Ta-1.8Nb alloy

The successful replacement of the present generation of corrosion-resistant materials (nitric acid-grade stainless steel and Ti) by Ti-5Ta-1.8Nb, which has better corrosion resistance, depends on its weldability characteristics. This article presents the results of a study on the fabrication, qualification, and microstructural characterization of the welds. Welding was carried out using the direct current electrode negative (DCEN) polarity tungsten inert gas (TIG) (manual) welding method with high-purity Ar shielding. Testing was carried out as per the ASME standard (section IX, welding and brazing). Qualification tests found that the weldment met the required properties. The weldment showed heterogeneous microstructures, which are rationalized based on differences in phase transformation mechanisms that are dictated by the thermal cycles experienced by various microscopic regions. The results, described in this article, confirm that the weldability of the developmental Ti-Ta-Nb alloy is excellent. A preliminary evaluation of the corrosion behavior of the welds showed rates comparable to that of the base metal, establishing that this alloy could be considered as an alternative material for use in highly corrosive environments.     

高能球磨制备TiB_2/TiC纳米复合粉体

研究了通过高能球磨制备ＴｉＢ２／ＴｉＣ纳米复合粉体的反应过程和机理,对粉体的显微结构进行了表征．实验结果表明,采用金属 Ｔｉ和 Ｂ４Ｃ为原料,在球磨过程中, ＴｉＣ先于 ＴｉＢ２形成．球磨５ｈ后Ｔｉ与Ｂ４Ｃ反应生成ＴｉＢ２和ＴｉＣ,在随后的长时间高能球磨过程中ＴｉＢ２和ＴｉＣ两相保持稳定．球磨 ３０ｈ后,直径约 ８ｎｍ的 ＴｉＣ纳米粒子分布在 １００～２００ ｎｍ的 ＴｉＢ２粒子中,形成均匀分布的纳米ＴｉＢ２／ＴｉＣ复合粉体．     

Synthesis of TiO2 nanopellet by TiCl4 as a precursor for degradation of RhodamineB

In the present investigation in order to promote TiO₂ pellet structure and its photocatalytic activity, two new precursors were synthesized in the powder and sol forms, using sol–gel method with precipitation of TiCl₄. Since TiO₂ pellets are normally synthesized by the commercial TiO₂ powder (DegussaP25), in this investigation and in the first step a new synthesized TiO₂ powder was produced and compared with DegussaP25. Subsequently, two types of pellet were made by the new synthesized powder and titania sol. The characterization of the synthesized TiO₂ powder and pellet were performed by XRD, FT-IR, scanning electron microscopy (SEM) and atomic force microscopy (AFM). The result showed that by the new procedure utilized here, without using any additive not only the surface area of the produced TiO₂ powder has been increased, but also the crystalline phase is completely in the anatase form. It was also found that the synthesized pellets by the sol precursor had better morphological structure than the synthesized pellets by theTiO₂ powder (either DegussaP25 or new synthesized powder). Ultimately, in order to evaluate photocatalytic activity of TiO₂ powders and pellet, degradation of RhodamineB was tested.     

Annealing process of fine grained co-stabilised (Y,Mg)-PSZ/MgAl2O4 ceramics

Abstract

Co-stabilised (Y,Mg) partially stabilised zirconia (PSZ) ceramics with MgAl₂O₄ spinel additions were produced, with industrial zirconia as the main starting material. Powders were prepared using a mechanical milling–mixing process. The effect of the annealing process on the mechanical properties, phase compositions, and microstructure of fine grained PSZ ceramics was investigated.     

半不连续切屑流动速度的系统分析及切屑变形的度量

本文借助影片运动分析仪,对用高速摄影记录的钛合金切屑沿前刀面的流动规律进行了研究,并用系统分析法进行了描述,推导出能反映半不连续切屑不均匀变形过程的动态衡量参数,同时也导出了度量此种切屑塑性变形的准静态参数——等效切削比。     

钛元素对铝钛合金中铝含量测定的干扰

在纯铝标样中加入相应的钛元素为标准,采用ＥＤＴＡ滴定法,测试钛元素对铝钛合金中铝含量测定的干扰。实验证明,钛对铝的测定干扰十分严重。文章给出了正确测定铝含量的方法。     

TiB_2/ZrB_2/SiC复合功能材料的微观结构与力学性能

采用放电等离子烧结工艺,制备TiB2/ZrB2/SiC复合功能材料。用X射线衍射仪和场发射扫描电镜分析观察复合材料的物相组成及微观形貌。并测试复合材料的抗弯强度、断裂韧性及硬度。结果表明:两次球磨后的TiB2/ZrB2/SiC粉体粒度较小(2~4μm),且分布较均匀,几乎没有团聚现象。烧结后的复合功能材料中有(TixZry)B2固溶体相生成。当加入ZrB2的体积分数为30%时,生成的(TixZry)B2固溶体在复合材料中起到了很好的晶粒细化与界面融合作用,所以TZS30复合陶瓷材料比TZS0复合陶瓷材料的抗弯强度和断裂韧性分别提高了119.8%和98.9%。利用TiB2/ZrB2/SiC复合陶瓷材料在高温摩擦作用下与氧的化学反应,可以实现自润滑。     

大塑性变形制备超细晶生物医用钛合金的研究进展

生物医用钛合金具有高强度、良好的耐蚀性能、较低的弹性模量、优异的生物相容性,已成为具有广阔应用前景的医用金属材料之一.与传统医用钛合金相比,超细晶医用钛合金具有更高的强度与更好的疲劳性能以及耐腐蚀性能.此外,超细晶钛合金可诱导骨组织向内生长,增加界面结合强度,加快骨修复进程,在硬组织修复材料领域具有广阔的应用前景.阐述了各种大塑性变形（Severe Plastic Deformation）法制备超细晶生物医用钛合金的研究状况与最新进展,指出了SPD法制备医用钛合金中存在的技术问题和发展方向,并展望了利用SPD法对生物医用钛合金改性将成为生物医用材料的研究热点.     

国内外海绵钛生产工艺现状

海绵钛生产的原则工艺流程为钛精矿→电炉熔炼钛渣→氯化→粗TiCl4精制→还原蒸馏→海绵钛。本文论述了该工艺流程中各海绵钛生产国所采取的独具特色的成熟技术。指出目前海绵钛生产发展的总趋势是：设备大型化、产能规模化、质量高纯化、控制自动化，而今后海绵钛生产的发展方向除研究探索熔盐电解法等新的技术方法外，重点还是对镁法更进一步完善，并探索低成本、连续化生产的途径。