The commercial application of low-cost titanium composites

Advanced powder-metallurgy (P/M) technology provides the key to a new class of low-cost, high-performance titanium-matrix composites known as CermeTi. Titanium carbide, the most successful particulate addition to date, imparts both strengthening effects and enhancement of the bulk modulus of elasticity when added to a titanium-alloy matrix, this article describes the process development and properties of these materials and describes the transfer of this technology from its early success in cost-effective defense applications to commercialization in highly competitive applications.     

Decomposition behavior of titanium hydride treated by surface oxidation

Titanium hydride attracts more attention as foaming agent in the fabrication of cellular metal materials.In order to meet most aluminum casting alloy's melting properties, the heat treatment processes for Ti H2 particles were investigated in a rotating device. In the present work,the most two important dynamic parameters, the treating temperature and oxidation interval, were taken under consideration. The decomposition behavior of titanium hydride was measured by differential scanning calorimetry(DSC) and the residual hydrogen content, morphologies and phase conversion were also characterized by hydrogen determinator, scanning electron microscopy(SEM), and X-ray diffractometer(XRD), respectively. The results show that the effect of temperature on the formation of oxidation film and decomposition behavior of TiH2 is more significant than that of oxidation time. The onset temperature and peak value of TiH2 decomposition shift from left to right through elevating temperature and extending time.Heat treatment process for TiH2 at 500 °C between 1 and5 h in air is favorable for preparing aluminum foam.     

高钛渣还原的氢化钛合金粉一步烧结制备高强钛合金（英文）

提出一种直接利用高钛渣制备高强钛合金的方法。先用镁粉还原高钛渣制备氧含量为1.3%(质量分数)的合金粉末,再将合金粉末在600 MPa压力下压制成小圆柱体,最后在氩气下烧结成钛合金产品。对还原粉末进行表征,研究烧结温度对烧结合金的烧后密度、抗压强度、显微组织和硬度的影响。结果表明,随着烧结温度由900℃升高至1200℃,钛合金的密度增加,孔隙率降低,实现较好的烧结致密化(1100℃为98.65%,1200℃为99.41%),在1100℃时硬度达到HV 655.7,压缩强度为1563 MPa。     

3D printing of titanium parts from titanium hydride powder by solvent jetting on granule beds

Titanium parts are produced by the “Solvent on granules 3D-Printing” technique (SG-3DP). Angular Titanium Hydride powders are used. A special purpose table-top machine, designed and built in a previous development, is used to print green parts, which are subsequently debinded, dehydrided and sintered in a muffle furnace. Porous electrode plates are produced with and without hole grids. The parts exhibit good shape preservation, with open interconnected porosities between 55 and 59%. The microstructure is characterized by optical metallography and scanning electron microscopy. In addition, experimental watch cases have been successfully printed and sintered. The results show the feasibility of using hydride powder for 3D-Printing of complex parts with good shape preservation.     

以稻壳为强化原料制备低成本钛合金的摩擦学性能

以稻壳热解产物为SiO₂源,通过粉末冶金法制备了Si和O固溶强化的低成本钛合金,并从磨损率、磨损表面形貌和磨屑成分等角度系统研究了其摩擦学性能和磨损机理。结果表明,随着SiO₂加入量的增加,Ti合金的体积磨损率显著降低,与硬度的变化规律吻合良好,同时磨损表面有三处变化,即犁沟的深度变浅、塑性变形程度降低和磨屑的尺寸变小和数量减少。SiO₂的加入使磨损机制从纯Ti的粘着和磨料磨损转变为磨料和氧化磨损,而磨屑尺寸的减小可归因于GCr15球和钛基体反复摩擦,导致磨屑的脆化。本文提供了一种使用农业废稻壳生产具有优良综合性能的钛合金方法,在降低钛合金成本的同时也有益于生态环境的保护。     

Fabrication of Fe-Ti alloys by pulsed current-assisted reaction from iron, manganese and titanium oxide or titanium hydride

Fe-Ti alloys were prepared by applying a pulsed electric current through compacted mixtures of iron, manganese and titanium oxide (with carbon) or titanium hydride (without carbon). After ball milling the mixture into a fine powder, the mixture was heated up to 1373–1573 K in a carbon mold by applying a pulsed electric current, and the temperature was maintained for 3–10 min. When TiO₂ was used as a starting material, TiC was formed. Fe was alloyed into FeTi and Fe₂Ti, with Ti also observed. When the C content was lowered to 8.136 wt%, the remaining C content after pulsed current application decreased to 4.64 wt%. When using TiH₂ as a starting material, Fe was alloyed into FeTi and Fe₂Ti, and Ti, Mn, Fe, and FeMn₂ were also observed. For a Fe-Ti alloy prepared using titanium hydride as a starting material, hydrogen content vs. absorption time curves were obtained at various numbers of cycles and temperatures.     

Using RABiTS to fabricate high-temperature superconducting wire

In order for many large-scale bulk applications of high-temperature superconducting materials to be realized, the cost/performance of the superconductors needs to be optimized. From a performance standpoint, a long, flexible, single-crystal-like wire is required; from a cost-and-fabrication standpoint, an industrially scalable, low-cost process is required. Both of these critical requirements are met by rolling-assisted biaxially textured substrates, a conductor-fabrication technique that employs simple, scalable, thermomechanical processing techniques to obtain a near-single-crystal-like, flexible metal substrate in arbitrary lengths on which epitaxial oxide buffer layers and superconductors are then deposited. For more information, contact A. Goyal, Oak Ridge National Laboratory, P.O. Box 2008, MS 6116, Oak Ridge, Tennessee 37831; (423) 574-1587; fax (423) 574-7659.     

Process and properties of hydride formed on gamma titanium aluminide during cathodic charging

A cathodic charging procedure was used to study the process of the formation of the hydride layer on gamma titanium aluminides. This electrolytic process was carried out at constant current densities of 1 and 2 A/m² for 24 h of charging in a 1N sulfuric acid solution. The hydride layer formed as a result of the charging process was observed using scanning electron microscopy. Nanohardness and microhardness of this hydride layer were also measured. Results show that the hydride forms initially as isolated islands and becomes continuous with increased charging time. The hydride layer is quite brittle and its degree of porosity increases from the metal surface outward. The thickness of the hydride layer also increases with charging current density. This is confirmed by the hardness measurements. EDS signals show the presence of the constitutive elements of gamma titanium aluminide in the hydride. ICPS analysis of the electrolyte indicates increasing metal content with increasing time of exposure probably as a result of the brittle hydride flaking off and falling into the electrolyte during the charging process.     

注凝成型技术的研究与进展

注凝成型技术是一种适用于复杂形状、大尺寸部件的近净尺寸成型技术,因其设备简单、工艺过程易控制、坯体密度均匀、强度高等突出优点而受到广泛关注;随着注凝成型技术的不断改进和完善,现已成为复杂形状零部件领域内近净成型的新工艺。本文简要介绍了注凝成型的技术原理和关键工艺,全面阐述了注凝成型技术在现代陶瓷材料、多孔材料、医用材料、复合材料及金属陶瓷等领域上的研究进展,并对注凝成型技术的主要难点以及广阔的应用前景进行了分析与展望,如:高固相含量、低粘度的粉体悬浮液料浆的制备;开发更为有效的分散剂;加强对多孔陶瓷应用的研究;开发新型的凝胶体系;快速推进工业化应用和加强对智能自动化控制设备的开发。     

Using friction stir processing to fabricate MgAlZn intermetallic alloys

Friction stir processing (FSP) is applied in mixing elemental thin sheets of Mg, Al, and Zn in various portions, resulting in hard intermetallic alloys with Vicker’s hardness in excess of 350. The Mg₃Al₂Zn₃ τ phase formed at 360 °C during FSP, coupled with some other binary or ternary phases of nano size, accounts for the high hardness.     

Microcapsules as an electronic ink to fabricate color electrophoretic displays

An encapsulated color electronic ink prepared by an in situ polymerization utilizing urea/melamine and formaldehyde resin as a wall material is presented. We have investigated the microencapsulation of magenta, yellow, and cyan polymer ball suspensions with white pigment for multi-color electrophoretic display implementation. The charged color pigments have been prepared to have a superior affinity for dielectric fluid by the physical coating of magenta, yellow, and cyan particles with functionalized polymers. TiO₂ nanoparticles were modified with poly(methyl methacrylate) copolymer for a microencapsulated electrophoretic display system, in order to reduce the density mismatch between nanoparticles and dielectric medium. The modified pigments were characterized by FTIR spectrometry, scanning electron microscope, and thermogravimetry analysis, respectively.     

Process analysis of direct laser melting to fabricate layered hybrid beads

The successful fabrication of layered hybrid beads by DLM process is limited by dissimilar melting ranges of different powders.For the application of DLM process into manufacturing industries,target mechanical properties of final product must be achieved.Process analysis was performed for the DLM fabrication of layered hybrid beads by using stainless steel (SS 316L) and titanium powders.For the analysis of fabrication characteristics,single hybrid bead was formed using SS316L powder onto the base plate and then Ti powder was melted onto the previous melted layer.In addition,multi-layer hybrid beads were fabricated for the analysis of the layering effects between them.From these studies,the effects of the processing parameters,such as laser power,scan rate and scan line spacing on surface morphology were characterized and optimum processing conditions for the DLM fabrication of layered hybrid beads were developed.     

氢化钛热分解特性与小孔径低孔隙率泡沫铝合金

采用金属管道氩载气流中的程序升温分解装置获得了氢化钛的热分解特性;运用位移传感器计算机系统获得了铝合金熔体保温泡沫化过程中孔隙率与保温发泡时间的关系;用图像分析法研究了氢化钛在铝合金熔体中均匀分散时间对泡沫铝合金熔体孔结构的影响;研究了不同孔隙率泡沫铝合金的压缩力学性能.结果表明:在940 K时,发泡剂氢化钛分解的30～80 s内,随着均匀分散时间的延长,铝合金熔体泡沫的孔隙率保持恒定,但孔数增多,孔径变小,由此获得了制备高比刚度、小孔径和低孔隙率泡沫铝合金的新途径.     

钛酸铝陶瓷的凝胶注模成型研究

利用琼脂凝胶大分子在水溶液中加热时溶解,冷却时凝固这一规律,研究了Al2TiO5陶瓷的凝胶注模成型工艺,探讨了琼脂含量和Al2TiO5的加入量对料浆流动性、制品的烧结、结构的影响规律.结果发现在固含量63%陶瓷料浆中引入约1.5%琼脂,成型干燥后不需要单独脱脂,即可获得表面光洁、结构均匀、致密、内部无明显缺陷的陶瓷部件.     

凝胶注模成型多孔氮化硅陶瓷

凝胶注模成型最初用来制备致密材料，本文则利用该方法来制备多孔氮化硅陶瓷。通过测试粉体的Zeta电位曲线以及加入分散剂（聚丙烯酸铵）时浆料的流变曲线，探讨了浆料的胶体特性和流变特性。分析了影响制品气孔率的几个因素。结果表明：粉体的等电点在pH为6附近，Zeta电位最大值在pH为10处。分散剂的加入使浆料的流体类型逐渐接近于牛顿流体。增加分散剂的含量和降低浆料的固含量可以提高制品的气孔率。     

凝胶铸成型亚微米级透明氧化铝光学性能研究

多晶半透明氧化铝陶瓷作为高压钠灯灯管和各种窗体材料等已在实际生产中得到广泛应用.但由于其强度低、耐腐蚀和透光性差无法满足新一代陶瓷金属卤素灯灯管高强度、高透明和耐腐蚀的要求.以高纯超细氧化铝粉作为原料,采用凝胶铸成型,并经过低温无压烧结和热等静压后处理,制各出了高强度亚微米级透明氧化铝陶瓷,实验表明该陶瓷在可见光区的全透比可达到75%,直线透过率最高可以达到37%.研究还发现无压预烧结温度对材料的微观缺陷以及最终的光学性能会产生重要的影响.     

水基凝胶注Ti-6Al-4V合金坯体

将凝胶注模工艺应用于金属Ti6Al4V合金粉末的成形,研究了高固相含量的Ti6Al4V合金粉末的料浆的制备,比较了金属浆料与陶瓷浆料的不同。结果表明粉末的颗粒形状是影响浆料固相含量的重要因素,浆料的固相含量随分散剂的增加而增加。最后制备出了固相含量为54%(体积分数,下同)的钛合金粉末浆料和形状复杂的坯体。坯体的抗弯强度随气雾化(GA)Ti6Al4V含量增加先增大后减小,随着坯体的固相含量增大而减小。当GA-Ti6Al4V含量为80%,固相含量为50%时生坯抗弯强度最大,为18.5 MPa。     

泡沫凝胶法制取陶瓷的气孔率影响因素研究

主要研究了泡沫凝胶法中的各工艺因素如搅拌速度、浆体粘度和浆体密度对气孔率的影响,并结合起泡形成理论,进一步引入雷诺数（Re）来衡量气孔率的变化.研究发现无论是改变搅拌速度、浆体粘度还是浆体密度,只要Re相同,则气孔率相同,并且在气孔率和雷诺数之间还存在着定量的函数关系.