Fabrication of Titanium Aluminides via Powder-Cored Wire Arc Additive Manufacturing: Microstructural and Mechanical Characterization

Herein, an innovative powder-cored wire arc additive manufacturing (PC-WAAM) process is proposed to fabricate γ-TiAl thin-walled intermetallic alloy. The metallography, phase composition, and mechanical properties at different thin-wall locations are characterized. The results show that the alternatively distributed layer-like microstructure composed of α₂ (Ti₃Al) and γ (TiAl) phases is obtained along the building direction. The content of α₂ phase exhibits the tendency of decreasing from the bottom to top region. This unique microstructure characteristic is closely related to the typical thermal cycling history during deposition. Moreover, the tensile strength and microhardness of the top region are lower than the middle and bottom region. In general, the current PC-WAAM technique shows promising capability of fabricating γ-TiAl intermetallic alloy with low cost. This work becomes a valuable reference for understanding the evolution mechanism of microstructure and paves the way for the flexible and customized additive manufacturing of γ-TiAl alloy.     

Advances in the fabrication of titanium based composites

Titanium alloy metal matrix composites reinforced with silicon carbide fibre are being evaluated for a range of highly loaded aerospace applications. Although expensive, if used selectively they can have a dramatic effect on performance and weight. The SMC has one of the strongest capabilities in Europe for the development and production of titanium fibre reinforced MMCs. Consisting of the DRA Sigma silicon carbide fibre manufacturing facility, producing fibre on a commercial basis, and the manufacture of titanium alloy MMCs in commercial quantities by the foil fibre route, and at pilot scale using the alternative matrix coated fibre route. In the foil fibre route a filament winding and fugitive binder method is used to produce a range of component shapes with excellent fibre distribution and consistent properties. The matrix coated fibre process is seen to have advantages over the alternative methods and is likely to become an important manufacturing route for titanium MMCs, particularly for exotic high temperature titanium alloys and intermetallics, and for shapes such as rings, tubes and shafts. As no titanium MMCs components have yet reached full production, it is unclear which of these fabrication methods will become commercially viable, if any. But, the choice is likely to be based on cost, availability and product quality.     

Phase relations in the Barium Titanate—Titanium Oxide System

Phase relations in the BaTiO₃—TiO₂ system were studied at temperatures above 1300°C in air. Quenching experiments were performed with high-purity reagents, and a new equilibrium phase diagram was constructed. Results include redetermination of the liquidus boundaries, the eutectic temperature, the melting or decomposition temperatures of the stable compounds in the system, the cubic—hexagonal transition in BaTiO₃, and the solid solubility of TiO₂ in BaTiO₃.     

工艺参数对TiO2碳热还原合成Ti（C,N）粉末的影响

本文探讨了ＴｉＯ２碳热还原法合成Ｔｉ（Ｃ，Ｎ）粉末过程中合成温度，保温时间，Ｎ２气流量，Ｃ／Ｔｉ比值等工艺参数的变化对粉末性状的影响，实验表明，Ｎ比Ｃ更易于Ｔｉ结合，改变工艺对数可调整Ｔｉ（Ｃ１－ｘＮｘ）的ｘ值。在１４００～１７００℃间可获得ｘ值的０．６～０．８５的Ｔｉ（Ｃ１－ｘＮｘ）粉末。     

Formation of CaO-TiO2-MgO-Al2O3 dual phase inclusion in Ti stabilized stainless steel

The formation of CaO-TiO2-MgO-Al2O3 dual phase inclusion in 321 stainless steel was investigated in the laboratory. The result indicated that the condition for the formation of CaO-TiO2-MgO-Al2O3 in 321 steel is [Ca]〉0.001wt%, [Ti]〉0.1wt%, and [A1]〉0.01wt%. The mechanism is the following： Al2O3 inclusion turns into CaO-Al2O3 after Ca-Si wire is fed into the molten steel; [Mg] is then obtained by reducing MgO in slag or crucible wall by [Al] and [Ti]; finally CaO-Al2O3 inclusion is changed into CaO-TiO2-MgO-Al2O3 by the reaction with [Mg], [Ti], and [O] in the molten steel simultaneously.     

基体拉伸法测试二氧化钛薄膜界面结合强度

利用热氧化法在工业纯钛表面形成氧化层,利用改进后的基体拉伸法研究了500和800℃加热1h所形成的氧化层和基体的结合强度,结果发现裂纹形貌与界面结合强度有关.500℃所形成的氧化层较薄,与基体的结合强度高,＞970MPa,裂纹方向与载荷轴向呈±45°;而800℃形成的氧化层较厚,与基体的结合强度差,＜495MPa,裂纹基本与载荷轴向垂直.     

钛合金表面激光熔覆材料研究进展

综述了目前钛合金表面激光熔覆材料的研究进展情况。提出了钛合金表面激光熔覆材料选择问题，以及现有材料体系存在的不足，为新材料体系的开发提供了一定的参考依据，使钛合金的综合应用前景更为广阔。     

还原-锈蚀法生产人造金红石技术现状及攀钢采用该工艺可行性分析

主要介绍了国内外还原-锈蚀法生产人造金红石工艺技术特点，并对攀枝花钛资源采用还原．锈蚀法生产沸腾氯化钛原料——人造金红石的可行性进行了分析探讨。     

钛板圆孔翻边成形极限与形状非轴对称化研究

为确定钛板圆孔翻边成形性能,揭示各向异性对制件形状和尺寸精度的影响,在室温和600℃用TC1MS1.5 mm钛合金坯料分别进行了圆孔翻边成形试验.结果表明:与室温冷翻边相比,热翻边可有效提高成形极限、消除冷翻边制件形状翘曲以及唇口部位椭圆化现象,在唇口边沿完好与破裂状态之间存在集中颈缩形式,而冷翻边则在底孔尺寸小于极限值时会直接发生破裂;冷、热圆孔翻边变形程度越大,则形状非轴对称化程度越严重.     

Effects of La(NO_3)_3 Treatment on Photocattalytic Activity of TiO_2 Films Prepared by Micro-Arc Oxidation

Effects of La(NO_3)_3 Treatment on Photocattalytic Activity of TiO_2 Films Prepared by Micro-Arc Oxidation