Precision casting of Ti-15V-3Cr-3AI-3Sn alloy setting

In this research, Ti-15V-3Cr-3Al-3Sn alloy ingots were prepared using ceramic mold and centrifugal casting. The Ti-15V-3Cr-3Al-3Sn setting casting, for aeronautic engine, with 1.5 mm in thickness was manufactured.The alloy melting process, precision casting process, and problems in casting application were discussed. Effects of Hot Isostatic Pressing and heat treatment on the mechanical properties and microstructure of the Ti-15V-3Cr-3Al-3Sn alloy were studied.     

The use of β titanium alloys in the aerospace industry

Beta titanium alloys have been available since the 1950s (Ti-13V-11Cr-3Mo or B120VCA), but significant applications of these alloys, beyond the SR-71 Blackbird, have been slow in coming. The next significant usage of a β alloy did not occur until the mid-1980s on the B-1B bomber. This aircraft used Ti-15V-3Cr-3Al-3Sn sheet due to its capability for strip rolling, improved formability, and higher strength than Ti-6Al-4V. The next major usage was on a commercial aircraft, the Boeing 777, which made extensive use of Ti-10V-2Fe-3Al high-strength forgings. Ti-15V-3Cr-3Al-3Sn environmental control system ducting, castings, and springs were also used, along with Ti-3Al-8V-6Cr-4Mo-4Zr (β-C) springs. Beta-21S was also introduced for high-temperature usage. More recent work at Boeing has focused on the development of Ti-5Al-5Mo-5V-3Cr, a high-strength alloy that can be used at higher strength than Ti-10V-2Fe-3Al and is much more robust; it has a much wider, or friendlier, processing window. This, along with additional studies at Boeing, and from within the aerospace industry in general will be discussed in detail, summarizing applications and the rationale for the selection of this alloy system for aerospace applications. This paper was presented at the Beta Titanium Alloys of the 00’s Symposium sponsored by the Titanium Committee of TMS, held during the 2005 TMS Annual Meeting & Exhibition, February 13–16, 2005 in San Francisco, CA.     

HYDROGEN EFFECT ON DEFORMATION BEHMIOR OF TITANIUM ALLOY AT HIGH TEMPERATURE

1.IntroductionContinuousfiberreinforcedtitaniummatrixcompositeshavepotentialapplicationatelevatedtemperature.Anewmethodhajsbeentriedbyoneofthepresentautho.s[1'21toalleviatethedeleteriousinterfacereactionbetweenthefiberandthematrix,whichislikelytooccurinthiscompositeduringfabrication.Previous.orb[llshowedthattitaniummatrixcompositecanachievefullconsolidationatrelativelylowtemperaturewiththeaidofhydrogenasatemporaryalloyingelement.Furtherstudyalongthisdirectionshouldbebasedonacomprehensiveunders…     

Spark anodizing behaviour of titanium and its alloys in alkaline aluminate electrolyte

Spark anodizing of titanium, Ti-6Al-4V and Ti-15V-3Al-3Cr-3Sn in alkaline aluminate electrolyte produces highly crystalline anodic films consisting mainly of Al₂TiO₅ with α- and γ-Al₂O₃ as minor oxide phases, irrespective of substrate composition. However, the apparent efficiency for film formation decreases in the following order: Ti-6Al-4V, titanium and Ti-15V-3Al-3Cr-3Sn. A large amount of aluminium species are incorporated from the electrolyte, probably by plasma-chemical reaction, and become distributed throughout the film thickness. This distribution indicates that the electrolyte penetrates near to the film/substrate interface through the discharge channels. Thus, the outwardly migrating aluminium ions under a high electric field can be present even in the inner part of the anodic films. Voids are developed at the film/substrate interface, particularly on the vanadium-containing alloys, reducing the adhesion of the anodic film to the substrate.     

Al元素对Ti-V-Cr系阻燃钛合金热强性影响的研究

制备了Ti-25V-15Cr-0．2Si和Ti-25V-15Cr-2Al-0．2Si2种阻燃钛合金，分别测试其在不同热暴露和蠕变工艺条件下的热稳定性能和蠕变性能，并观察了组织。结果表明，Al元素提高了Ti—V-Cr系阻燃钛合金的室温力学性能，降低了热稳定性能和抗蠕变性能；在实验的热稳定和蠕变工艺参数下，2种合金中只存在a相和Ti5Si3相，没发现其他过渡相和中间化合物；在热暴露和蠕变过程中，组织稳定性降低，Al元素的添加促进了a相和Ti5si，相的析出，降低了Ti-V-Cr系阻燃钛合金抗蠕变性能和热稳定性能。     

粉末冶金碳化物强化铌合金组织演变及其力学行为

采用机械球磨与热压烧结相结合的粉末冶金法对不同球磨时间Nb-35Ti-6Al-5Cr-8V-5C合金的粉末变形行为,微观组织结构和力学行为进行研究。结果表明:随着球磨时间的增加,Nb-35Ti-6Al-5Cr-8V-5C复合粉末中的块状金属颗粒首先变形为片状后在碰撞挤压作用下破碎成絮状,TiC粉末均匀的分布于片状金属粉末表面;Nb-35Ti-6Al-5Cr-8V-5C合金由Nbss和(Nb,Ti)C两相构成,各合金碳化物体积分数均为11%左右,Ti元素主要分布于Nbss晶界和碳化物内,Al、Cr、V元素主要分布于Nbss晶粒内,Nbss和(Nb,Ti)C相尺寸均随球磨时间增加而尺寸减小;Nbss晶粒细化及强化相碳化物弥散化导致合金的室温压缩力学性能和塑性变形能力显著提高,压缩变形后合金Nbss与碳化物具有良好的界面结合能力,但是碳化物内部存在明显的近似平行分布的裂纹;数据对比表明,粉末冶金法制备Nb-35Ti-6Al-5Cr-8V-5C合金的力学性能优于电弧熔炼法。     

Diffusion bonding/superplastic forming of Ti-6Al-6V-2Sn/SUS 304 stainless steel/Ti-6Al-6V-2Sn

The superplasticity of the Ti- 6Al- 6V- 2Sn alloy for different temperatures was evaluated by single-sheet free blowing. The optimal superplastic temperature for the Ti- 6Al- 6V- 2Sn alloy was found to be 850 °C. Diffusion bonding of Ti- 6Al- 6V- 2Sn and 304 stainless steel was carried out in a vacuum. The interface of both bonded alloys was examined by EPMA. The concentration profile of Ni exhibited a peak at the interlayer and a valley adjacent it, whereas that of Cr exhibited a peak where Ni showed the valley. X- ray diffraction (XRD) analyses showed that the Fe ₂ Ti, NiTi, and CrMn Intermetallic compounds and the Cr element formed at the interface. The thickness profiles of the blown specimens were measured and compared with theoretical calculations.     

油气开采用钛合金石油管材料耐腐蚀性能研究

选取5种油气开发常用钛合金材料(Ti-6Al-4V、Ti-6Al-4V-0.1Ru、Ti-6Al-2Sn-4Zr-6Mo、Ti-3Al-8V-6Cr-4Zr-4Mo和Ti-5.5Al-4.5V-2Zr-1Mo)为研究对象,使用高温高压釜模拟国内典型严酷服役工况环境,研究了不同钛合金材料耐均匀腐蚀、局部腐蚀、点蚀、应力腐蚀开裂(SCC)及缝隙腐蚀的性能,通过使用扫描电镜和能谱分析等手段对腐蚀形貌和腐蚀产物进行了分析,并使用电化学方法对不同合金的耐腐蚀机理进行了研究。结果显示,在所测试工况条件下,所有钛合金材料腐蚀反应均为阳极控制过程,均匀腐蚀速率均低于0.001mm/a,并且对应力腐蚀开裂均有良好的抗力。Ti-6Al-4V和Ti-5.5Al-4.5V-2Zr-1Mo合金出现明显的点蚀和缝隙腐蚀问题。对腐蚀机理研究表明,在工况条件温度下,随着pH值的降低,所有钛合金均发生自腐蚀电位降低,极化电阻减小,腐蚀电流增大,耐腐蚀性能下降,其中Ti-6Al-4V耐腐蚀性能下降的最为明显,研究结果为油气开发工况下钛合金石油管的选材和缝隙腐蚀问题防治提供理论基础。     

粉末冶金Nb-35Ti-6Al-5Cr-8V合金组织演变及其力学行为

采用粉末冶金法对不同球磨时间的Nb-35Ti-6Al-5Cr-8V合金机械合金化粉末塑变行为,热压烧结材料的微观组织结构和力学行为进行了研究。研究结果表明：塑性良好的Nb-35Ti-6Al-5Cr-8V粉末随着球磨时间增加首先变形为大尺寸的片状、后经持续的加工硬化破碎成絮状;热压烧结能够制备微观组织可控晶粒细化的Nb-35Ti-6Al-5Cr-8V合金,合金由单一的Nbss相构成,Ti、Al、Cr、V元素固溶引起Nb晶格尺寸减小0.0685 ?;随着球磨时间增加合金晶粒明显细化进而显著提高了合金的维氏硬度和室温压缩强度,其变化符合材料硬度和强度的Hall-Petch规律。粉末冶金制备Nb-35Ti-6Al-5Cr-8V合金的各项力学性能明显优于熔铸法制备合金。     

合金化对消失模铸造高锰钢凝固组织的影响

通过对ZGMn13进行多元合金化和凝固过程工艺控制,力求直接在铸态下获得理想的全奥氏体组织。采用消失模负压实型铸造工艺制备铸态高锰钢试样,借助光学显微镜、X射线衍射仪(XRD)、能谱分析仪和硬度测试仪等检测设备,分析了合金化前后铸态高锰钢凝固组织特征。结果表明,当合金元素添加量为0.33Cr-0.38Mo-0.06V-0.05Ti-0.66Ni时,凝固组织中只有部分碳化物析出;当合金元素添加量达到0.72Cr-0.70Mo-0.14V-0.13Ti-1.23Ni时,高锰钢在铸态下获得了全奥氏体组织;随合金元素加入量的进一步增加,铸态凝固组织均为全奥氏体组织。奥氏体晶粒度随合金元素加入量的增加而减小,硬度随合金加入量的增加而增加。     

Hot-salt-stress-corrosion cracking of titanium alloys

The H.S.S.C.C. (Hot-Salt-Stress Corrosion-Cracking) of certain titanium alloys (Ti 5 Al-2.5 Sn; Ti-6 Al-4 V; Ti-8 Al-1 Mo-1 V; Ti-13 V-11 Cr-3 Al) was investigated both by means of exposure experiments with U-bend specimens and by means of electrochemical experiments with a macro-couple model proposed by the authors of this paper. With this model it has been possible to confirm that there is an electrochemical mechanism for this form of corrosion and to perfect a system capable of revealing the incubation period of cracks as a function of environmental, metallurgical and mechanical factors with good reproducibility and accuracy.     

NUMERICAL SIMULATION OF INDUCTION SKULL MELTING PROCESS FOR TITANIUM-ALUMINIUM BASE ALLOY

The mathematics model for temperature field of water-cooling copper crucible induction skull melting process was established. The program for simulating temperature field of melting process was developed with finite element method. The temperature field of the melting process for Ti-47Al-2Cr-2Nb aUoy was calculated. During melting period, the temperature is raised gradually along radius augmentation direction. The elements of the charge near the crucible wall are molten first. The center elements of the charge are molten last. The melting time of the center element is just that of all the charge melting. The melting time of Ti-47Al-2Cr-2Nb alloy is 15min. In which, the charge was heated by low power 80kW for 9min and by high power 300kW for 6min. When melting Ti-47AI-2Cr-2Nb aUoy,the loading power is nearly direct proportion to melt temperature. Increasing loading power may raise melt temperature. The best melting power of Ti-47Al-2Cr-2Nb alloy is 305-310kW. This is identical with the melting test and has guidance sense to the melting process of actual titanium aUoy.     

Ti-15-3合金热变形固溶显微组织的多重分形研究

以Ti-15-3(Ti-15V-3Cr-3Sn-3Al)合金热变形固溶再结晶显微组织的金相照片作为研究对象,基于Matlab软件平台,自行开发了图像处理及多重分形分析程序,实现了从材料组织结构形貌图像上提取其相应的概率测度和标度指数的功能,并计算了多重分形谱.结果表明,在当前的观测尺度范围内,Ti-15-3合金热变形固溶再结晶显微组织具有多重分形特征.且随着再结晶晶粒尺寸的增大和形变晶粒尺寸的减小,多重分形谱宽△α减小,表明显微组织分布越均匀.另外,在再结晶晶粒尺寸相差不大时,随着再结晶百分数的增大,最大最小概率子集维数的差值△f增加,再结晶晶粒为主导分布,显微组织更为细化均匀.这些研究为材料组织结构的定量表征提供了新的思路.     

Effect of Gas Composition on Nitriding and Wear Behavior of Nitrided Titanium Alloy Ti-15V-3Cr-3Al-3Sn

Titanium alloy, Ti-15V-3Cr-3Al-3Sn was nitrided at different temperatures with low pressure plasma with 100% nitrogen, and nitrogen diluted with hydrogen and argon. The nitrided layers were characterized for hardness, structure, and composition. Nitrided samples show weight gain that depended on temperature and duration of nitriding. EDS results show that intake of nitrogen is significant at temperatures above 750 °C. Hydrogen dilution increases intake of nitrogen. Samples nitrided with hydrogen dilution have lower surface roughness and higher nitrogen concentration. Depth profiling by XPS shows the formation of nitride in the near-surface region and also that nitrogen concentration in the interior of the nitrided layers is higher at higher temperatures. Micro Raman shows that formation of nitride takes place at higher temperatures. XRD shows that the nitrided layers consist predominantly of alpha Ti and Ti₂N. This is reflected in the hardness increase and hardness profile in the nitrided samples. The low intake of nitrogen by the alloy is attributed to the low solubility of nitrogen in beta alloy and low diffusion coefficient of nitrogen. Reciprocating wear studies showed a lower coefficient of friction and lower wear loss for nitrided samples compared to that of substrate.     

Dynamic recovery and recrystallization in titanium alloys by hot deformation

The microstructural change of β titanium alloys, Ti-15V-3Cr-3Sn-3Al and Ti-10V-2Fe-3Al, and an (α+β) titanium alloy, Ti-6Al-4V, during hot deformation at temperatures in β single-phase and (α+β) two-phase regions was studied. For the β titanium alloys, dynamic recovery takes place dominantly within β grains during deformation in the β single-phase region although some discontinuous dynamic recrystallization occurs along β grain boundaries. The size and fraction of recrystallized β grains increase as strain rate decreases or the deformation temperature rises.     

Two-step plasma electrolytic oxidation of Ti-15V-3Al-3Cr-3Sn for wear-resistant and adhesive coating

Ti-15V-3Al-3Cr-3Sn (Ti-15-3) is one of the important practical titanium alloys with high cold deformability and high mechanical strength, but its wear resistance is poor. This paper reports the formation of wear-resistant and adhesive ceramic coatings on Ti-15-3 by two-step plasma electrolytic oxidation (PEO). The PEO of Ti-15-3 has been carried out first in alkaline aluminate electrolyte to form a wear-resistant oxide layer and then in acid electrolyte containing both phosphoric acid and sulfuric acid to improve adhesion of the coating. The coating formed in the alkaline aluminate electrolyte is more than 10 μm thick, and highly crystalline. The main phase is Al₂TiO₅. This coating shows high wear resistance, but is not adherent to substrate due to the development of a number of voids and pores in the oxide layer close to the substrate. A new oxide layer with amorphous structure is formed next to the substrate in the subsequent PEO in the acid electrolyte, during which the voids are filled with a new oxide formed in the acid electrolyte, reducing the porosity. As a consequence, the adhesion of the coating is markedly improved without deteriorating the high wear resistance.     

硼含量及冷却速度对TiAl合金十字形铸件组织的影响

采用真空感应磁悬浮熔炼法制备Ti-47Al-2Cr-2Nb-xB(x=0,0.15,0.8,1.5)(at%)十字形不同壁厚(2、5、10、20mm)的铸件。借助体视显微镜、扫描电子显微镜(SEM)对铸件的组织进行分析,研究硼含量和冷却速度对铸件硼化物形态、晶粒细化效果的影响。结果表明:硼含量越高,冷却速度越快,细化效果越好。随着硼含量的增加,硼化物的形态从弯曲条带状逐渐转变为短棒状或片状。Ti-47Al-2Cr-2Nb-0.8B铸件硼化物尺寸随冷却速度的降低而减小,Ti-47Al-2Cr-2Nb-0.15B和Ti-47Al-2Cr-2Nb-1.5B铸件硼化物随冷却速度的变化规律不明显。     

Cr元素对Ti-V-Cr系阻燃钛合金热暴露力学性能的影响

研究了Ti-25V-15Cr-0.2Si和Ti-25V-10Cr-0.2Si两种阻燃钛合金在不同热暴露条件下的热稳定性能.结果表明:Cr元素对Ti-V-Cr系阻燃钛合金的组织有较强细化作用,强化合金室温力学性能;随Cr元素含量的降低,合金在热暴露过程中析出的第二相减少,合金热稳定性能优化.此实验现象与Cr元素在钛合金中属于共析元素的性质有关.     

Thermophysical properties of Ti-5Al-5V-5Mo-3Cr-1Zr titanium alloy

The thermophysical properties of the Ti-5Al-5V-5Mo-3Cr-1Zr titanium alloy in a wide range of temperatures from room temperature to 1000°C have been studied by the methods of differential scanning calorimetry, the laser flash method, and dilatometry. The obtained data on heat capacity, thermal diffusivity, and thermal expansion have been used for calculating coefficient of thermal conductivity. The sequence and temperatures of structural transformations during heating of the alloy have been established. It has been shown that the studied alloy possesses a coefficient of thermal conductivity that is 3.5–4 times smaller than that of pure titanium.     

B、Y及冷却速度对Ti-47Al-2Cr-2Nb合金组织的细化作用

研究了微量元素B、Y和冷却速度对Ti-47Al-2Cr-2Nb合金组织的复合细化效果。结果表明,在水冷铜坩埚磁悬浮真空感应熔炼和Y2O3型壳精密铸造条件下,B元素能够有效细化Ti-47Al-2Cr-2Nb铸件的晶粒尺寸,使其由粗大的柱状晶变为细小的等轴晶组织,但没有起到细化片层间距的明显作用。B、Y复合细化可以在B元素细化效果的基础上进一步细化片层团尺寸,同时显著细化片层间距。在壁厚为2～20mm范围内,Ti-47Al-2Cr-2Nb-0.8B-0.3Y铸件的宏观组织均为等轴晶;且随着厚度的增加,等轴晶尺寸逐渐增大。适当降低型壳预热温度也有助于获得细小的片层组织。