Ti50Al和Ti45Al8Nb合金高温初期氧化行为

利用SEM、XPS和AES研究了Ti50Al和Ti45Al8Nb(原子分数,%)合金在900 ℃空气中的初期氧化行为.结果表明:Nb的加入显著提高了合金的抗氧化性.氧化90 min后,Ti50Al合金表面为粗大的富TiO2颗粒,冷却过程中部分表层氧化膜脱落,脱落后内层为多孔、疏松的Ti和Al的混合氧化物(可能有氮化物);Ti45Al8Nb合金表面生成很薄的氧化膜,其外层为细小富Al2O3颗粒,Nb只存在于内层(富TiO2层)和混合层,在外层Al2O3内没有发现,Nb5 取代TiO2中的Ti4 ,降低氧空位浓度从而减慢氧的向内扩散,抑制TiO2的生成,同时促进了外层纯Al2O3层的形成,该层阻碍氧以及合金元素的进一步扩散.     

Al对高温合金高温抗氧化性能的影响

通过加入Al改善高温合金氧化膜的稳定性,并辅以微量强化元素Nb与合理的热处理工艺来提高高温合金抗氧化性。在真空感应熔炼炉中熔炼合金,利用扫描电镜、X射线衍射仪研究了Al元素对高温抗氧化性能的影响。结果表明:Al的加入提高了钢的抗氧化性,但含5%Al试样的氧化膜表面出现大量裂纹;合金氧化膜主要是由Cr2O3和具有尖晶石结构的FeCr2O4、Fe3O4以及少量Al3Fe5O12组成。     

不锈钢热浸镀铝后的抗氧化性能

通过对普通奥氏体不锈钢1Cr18Ni9Ti热浸镀铝（Al）＋混合稀土（RE）,分析了热浸镀铝不锈钢的高温长时间（500h）抗氧化性能。结果表明,热浸镀铝不锈钢在700℃、800℃的氧化增重较相同条件下未镀铝不锈钢的氧化增重高;1000℃氧化时,在热浸镀铝不锈钢的表面生成完整的α－Al2O3,使镀件表现出良好的长时间抗氧化性能,因而可以在此温度下长期使用。     

Thermal cycling of Ti46Al8Nb1B

The effects of thermal cycling on the mechanical properties and microstructure of a TiAl-based alloy (Ti46Al8Nb1B) have been investigated for samples with and without an imposed external stress. The temperature range (300–800 °C) and stress (0 or 300 MPa) were chosen to reflect likely industrial usage. Unstressed samples showed no significant effect of thermal cycling. Thermal cycling with external stress is found to reduce the yield stress, ductility and UTS and to increase the amount of primary creep. The microstructural changes include dislocation and twin generation, ₂/γ ledge formation, dissolution of ₂ lamellae and microcrack formation. The changes in mechanical properties are interpreted in terms of the changes in microstructure.     

表面微晶化对Fe_3Al抗高温氧化性能的影响

研究了高能量密度等离子体表面微晶化处理对Ｆｅ３Ａｌ在１０００℃空气中氧化动力学及氧化膜结构和性质的影响。结果表明，表面微晶化使氧化物形核率极大提高，形成了薄而致密的微晶氧化膜，缩短了过渡氧化时间，促进了合金中Ａｌ的选择氧化，改善了氧化膜的塑性和粘附性，显著提高了Ｆｅ３Ａｌ的抗高温氧化性能。     

(Ti,Al)N梯度涂层高温氧化表面形貌分析

利用MIP-8-800型电弧离子镀设备,在发动机压气机叶片材料1Cr11Ni2W2MoV不锈钢表面沉积了(Ti1-xAlx)N梯度纳米涂层。对其进行了700℃不同何温时间高温氧化性能实验。采用XL-30FEG型扫描电子显微镜对氧化后的涂层表面进行了观察分析。观察结果表明,(Ti1-xAlx)N梯度纳米涂层中,当x≥0．25时,所形成的A12O3氧化层是致密完整连续的,具有良好的抗高温氧化性能。     

铝对马氏体抗磨耐热钢高温抗氧化性能的影响

通过650℃和800℃下的氧化增重测量、氧化动力学分析、氧化膜XRD分析和氧化膜表面EDS分析,研究了铝对马氏体抗磨耐热钢高温抗氧化性能的影响规律。结果表明:随着含铝量的增加,抗磨耐热钢的氧化增重不断减小。含铝量为1.97%时,试样在650℃下的平均氧化速率为0.009 5 g·m-2·h-1,在800℃下的平均氧化速率为0.028 5 g·m-2·h-1,氧化产物由Al2O3、Cr2O3、Fe(Cr Al)2O3和Fe(Cr Al)2O4组成。铝含量大于1.47%时,Al2O3氧化膜连续且致密,试样在650℃和800℃下均为完全抗氧化钢。     

Microstructures and tensile properties of massively transformed and aged Ti46Al8Nb and Ti46Al8Ta alloys

Fully massively transformed samples of Ti46Al8Nb and Ti46Al8Ta have been HIPped (hot isostatically pressed) in the (α + γ) phase field in order to generate a fine convoluted microstructure and their tensile properties compared with those of samples with coarse lamellar microstructure. It has been found that the yield strengths and ductilities of the microstructurally refined samples were significantly improved with respect to those with coarse microstructures. The proof stresses of the microstructurally refined samples of the Ta- and Nb-containing alloys were almost identical (550 MPa) but the ductility in the Ta-containing alloy is about double that of the Nb-containing alloy, reaching values of up to 1.1% plastic strain. However, there is significant scatter in the elongation in both alloys, which in the case of the Ta-containing alloy has been shown to be associated with segregation which hinders the massive transformation and leads to the formation of some large grains. These observations are discussed in terms of the practicality of using massively transformed and heat-treated cast alloys in engineering components and in terms of the factors controlling the tensile behaviour.     

DEFORMATION STRUCTURES IN A Ti45Al 10Nb ALLOY AT ROOM TEMPERATURE

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铌合金表面高温抗氧化涂层

介绍了铌合金表面高温抗氧化涂层的4大体系——耐热合金涂层、铝化物涂层、硅化物涂层和贵金属涂层的组成、特点及制备条件。我国研究人员围绕飞机发动机涡轮叶片和火箭发动机燃烧室及尾气喷管用铌合金的防护进行了大量研究工作，研制的高温抗氧化涂层已经用于49kN推力发动机铌合围裙和姿态控制铌合金喷管。通过研究认为，PVD和传统熔烧工艺相结合的新工艺及纳米涂层技术是今后铌合金表面高温涂层制备的研究方向。     

原位自生Ti2AlC/Ti-40Al复合材料的高温氧化行为

利用海绵钛、高纯铝与TiC/Al中间合金反应.采用非自耗电弧熔炼工艺,原位合成Ti2AlC/Ti-40Al复合材料.研究复合材料在900℃空气中的恒温氧化行为,分析不同的增强体含量对复合材料氧化动力学行为的影响.并通过SEM、EDS及XRD对氧化层的表面形貌、成分及横断面的显微结构进行分析.结果表明,复合材料的氧化动力学曲线介于抛物线和对数规律之间.且随着碳化物含量的增加,复合材料的抗氧化性呈下降趋势.研究发现.氧化表面为堆砌生长的柱状六方晶,主要为金红石型的TiO2;氧化断面为明显的三层结构,最内层氧化膜基本上是在碳化物颗粒周围产生的,中间层为Al2O3和TiO2的混合物层,外层主要为TiO2.     

锰对Ti－45Al－10Nb合金的组织和性能的影响

研究了Ｍｎ对Ｔｉ－４５Ａｌ－１０Ｎｂ（原子分数）合金铸态组织和１１００℃再结晶组织的影响以及Ｍｎ对于Ｔｉ－４５Ａｌ－１０Ｎｂ合金力学性能的影响。结果表明，Ｍｎ能促进Ｔｉ－４５Ａｌ－１０Ｎｂ合金的再结晶过程，并改善合金的力学性能     

The formation of grain boundary gamma during cooling of Ti46Al8Nb

Samples of Ti46Al8Nb have been cooled from the alpha phase field at 4 °C/min and subsequently oil quenched; others have been end-quenched. The microstructures have been examined using optical and analytical scanning and transmission electron microscopy. It has been found that cooling to only 30 °C below the transus results in the formation of significant amounts of grain boundary gamma. This grain boundary gamma can grow into the alpha matrix; it can nucleate alpha/gamma lamellae, or massive gamma, or gamma/gamma lamellae; it can influence the fracture behaviour in massively transformed samples that have been heat treated to refine the microstructure. The factors that influence which structure is associated with the grain boundary gamma are investigated and it is clear that the cooling rate is the dominant factor. The significance of these observations is discussed in terms of the properties of cast samples which have been heat treated by precipitating alpha within the massive gamma.     

Cr18Ni30Mo2Al3Nb合金的高温抗氧化性能

采用称重法测得Cr18Ni30Mo2Al3Nb合金在不同温度下的高温氧化动力学曲线。结果表明,该合金的氧化曲线遵循抛物线氧化规律,具有优良的抗氧化性能。利用扫描电镜、X射线衍射的方法对氧化膜表面形貌及结构进行研究,该合金在3个温度下氧化膜完整致密,700℃氧化膜主要由Fe和Cr的混合氧化物(Fe0.6Cr0.4)2O3和少量Al的氧化物组成;800℃氧化膜主要是Al和Cr的混合氧化物(Al0.9Cr0.1)2O3和少量Al2O3及少量Fe的氧化物;900℃氧化膜主要是(Al0.9Cr0.1)2O3和Al的氧化物,还含有少量Fe(Cr,Al)2O4和MnFe2O4。     

几种热浸镀层抗高温氧化性能的比较

以Q235钢和1Cr18Ni9Ti不锈钢为典型钢种,分别采用水溶剂法和钝化法,制成Al、55%Al-Zn和Zn的热浸镀层,并连同Q235钢和1Cr18Ni9Ti不锈钢裸材,进行了从600－1150℃系统的循环加热对比试验,讨论了在本试验条件下各镀层的最高使用温度,并计算了它们的理论使用寿命。     

The influence of interrupted cooling on the massive transformation in Ti46Al8Nb

Samples of Ti46Al8Nb (at%) have been cooled slowly from the alpha phase field to different temperatures within the alpha plus gamma phase field and then cooled rapidly to room temperature, using iced brine as a quenching medium. The resultant microstructures have been characterised using optical and analytical electron microscopies. The structures consist of mixtures of gamma/alpha 2 lamellae, formed during slow cooling through the two phase fields, together with retained alpha 2 and massively transformed gamma, formed on quenching. The majority of the massive phase formed in these samples nucleates on lamellae formed at alpha grain boundaries after they have grown across the grain boundary so that they have no simple orientation with the alpha matrix. In this case EBSD (Electron back scattered diffraction) has shown that the massively transformed gamma inherits the orientation of the lamellar gamma, upon which it nucleates and is thus also incoherent with the surrounding alpha matrix. When massively transformed gamma nucleates on coherent defects, such as stacking faults or lamellae within grains, it also has no orientation relationship with the alpha and thus forms a high angle incoherent boundary, allowing rapid growth. The detailed observations are discussed in terms of the behaviour of the factors which govern the nucleation of massive gamma and the propagation of the transformation front between the massive phase and the parent alpha.     

Ti6Al7Nb和Ti6Al4V合金的热氧化行为

在600～900℃温度下,0.5～72 h时间范围内空气气氛下对Ti6Al7Nb进行热氧化,根据增重曲线计算其氧化动力学规律,利用XRD、XPS分析表面氧化层的相组成、成分和价态,并以Ti6Al4V合金做为比照.结果表明,Ti6Al7Nb合金较Ti6Al4V合金抗氧化能力更强.同等氧化条件下,Ti6Al7Nb合金的氧化速率常数(k)更小.对短时间(1 h)氧化的样品的表面分析显示:各合金元素均以最高价态或稳定价态存在,其中Al和V被富集,而Nb则贫化;另外,Ti6Al7Nb合金和Ti6Al4V合金氧化层主要由金红石型TiO2(R-TiO2)组成,Al2O3相仅出现在900 ℃Ti6Al4V合金样品中.     

High-temperature oxidation of Ti3Al−Nb alloys

Titanium aluminide (Ti₃Al–Nb) has potential for high-temperature applications because of its low density and high-temperature strength. This research is aimed at improving the high-temperature oxidation resistance of a Ti₃Al–Nb alloy by modification of its composition. The oxidation rates of Ti₃Al–Nb alloys were measured from 600 to 900°C in air. The oxide layer was examined by X-ray diffraction, scanning electron microscopy, and electron probe microanalysis. The experimental results reveal that alloys with added Nb tend to form denser oxide layers and that oxidation rate can be reduced by increasing Nb content (up to 11 at.% in this study), which is in good agreement with other investigators. The only exception is a Ti₆₅Al₂₅Nb₁₀ alloy, which shows better oxidation resistance than the commercial Ti₆₅Al₂₄Nb₁₁ alloy. The oxidation resistance of Ti₆₅Al₂₅Nb₁₀ alloy can also be improved slightly by the addition of small amounts of Si or Cr. An increase in the oxidation resistance of Ti₆₅Al₂₅Nb₁₀ alloy containing Y was observed at 900°C but not at 800°C or below. The parabolic oxidation rate equation is adequate to describe the high-temperature oxidation reaction of the Ti₃Al–Nb alloys in the atmosphere.     

Al对ZG40Cr25Ni20抗磨耐热钢高温抗氧化性的影响

在ZG40Cr25Ni20抗磨耐热钢中加入不同含量的Al,在900℃和1100℃下分别进行循环高温抗氧化性试验。通过不同温度下氧化增重测量、氧化动力学分析,以及试验后试样形貌观察,得出了Al对ZG40Cr25Ni20高温抗氧化性能的影响规律,结果表明适量的Al能明显提高ZG40Cr25Ni20的高温抗氧化性。     

溶胶-凝胶法制备薄膜材料抗高温氧化性能研究

制备了SiO2、ZrO2和添加不同成分的siO2-ZrO2复合溶胶，研究了在Cu／Ni上浸涂不同溶胶后形成膜层的抗高温氧化性能，探讨了不同膜层对Cu／Ni在800℃、900℃C下高温氧化规律的影响。结果表明，这些膜层很好的改善了Cu／Ni的抗高温氧化性能，而且向SiO2-ZrO2复合溶胶中添加铈、钇等稀土元素以及ZrO2纳米粉，可以进一步改善SiO2-ZrO2凝胶膜层的抗高温氧化性能。