不同结构及成分的Al3Ti合金成键特征的分析

利用Ｘ射线光电子能谱法分析了Ａｌ３Ｔｉ系合金的成键性质。Ｄ０２２型Ａｌ３Ｔｉ成键性质的各向异性有利于稳定Ｄ０２２结构，Ｌｌ２型Ａｌ３Ｔｉ成键方式呈各向同性。Ａｌ６７Ｔｉ２５Ｍｎ８合金中Ａｌ－Ｔｉ键与Ａｌ６７Ｔｉ２５Ｎｉ８合金相比具有球化程度高，方向性小的特点，有利于提高塑性。     

Ti—47Al—2Mn—2Nb合金低温静态和动态拉伸性能及硼的影响

采用常规拉伸和Ｈｏｐｋｉｎｓｏｎ拉杆技术,研究具有近全片层组织形变Ｔｉ－４７Ａｌ－２Ｍｎ－２Ｎｂ合金１８０Ｋ下静态和动态拉伸性能及其受硼的影响。发现Ｔｉ－４７Ａｌ－２Ｍｎ－２Ｎｂ和Ｔｉ－４７Ａｌ－２Ｍｎ－２Ｎｂ－１Ｂ合金１８０Ｋ下的拉伸强度均比室温度。     

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     

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。     

钛的电阻钎焊技术研究

研究了Ｔｉ－２４Ａｌ－１１Ｎｂ－２Ｓｉ和Ｔｉ－２４Ａｌ－１１Ｎｂ－５Ｓｉ金属间化合物合金的热轧组织与性能,结果发现：随着变形量的增加,两种合金第二相Ｔｉ５Ｓｉ３变得细小且趋向于均匀分布。变形量越大,合金的室温四点弯曲程度越大,含Ｔｉ５Ｓｉ３较多的Ｔｉ－２４Ａｌ－１１Ｎｂ－５Ｓｉ合金的弯曲强度较高。两种合金的室温弯曲断口形貌均为准解理形式,两相界面结合较强。高温拉伸试验表明：随变形量的增大,Ｔｉ－２４Ａｌ－１１Ｎｂ－２Ｓｉ合金的拉伸强度和塑性都增加。Ｔｉ－２４Ａｌ－１１Ｎｂ－５Ｓｉ合金由于变形量较大和较高的强化相体积含量,拉伸强度明显较Ｔｉ－２４Ａｌ－１１Ｎｂ－２Ｓｉ合金的为高,但塑性却大为降低     

Ti—47Al—2Mn—2Nb—0.8TiB2合金韧脆转变温度及其应变速率敏感性

采用拉伸试验,研究了不同应变速率（１０＾－５－１０＾－１ｓ＾－１）下温度对含体积分数为０．８％的ＴｉＢ、具体近全片层组织的Ｔｉ－４７Ａｌ－２Ｍｎ－２Ｎｂ金属间化合物的屈服强度和延伸率的影响,得到合金韧脆转变温度随应变速率升高而升高的变化关系,确定这种ＴｉＢ２的ＴｉＡｌ合金的韧脆转变激活能为２５６ｋＪ／ｍｏｌ。这一数值低于无ＴｉＢ２的ＴｉＡｌ合金韧脆转变过程可能受位错攀移机制控制。     

Al67Mn8Ti24Nb1金属间化合物亚稳态粉末热压成形后的组织结构及性能

铸态复相Ａｌ６７Ｍｎ８Ｔｉ２４Ｎｂ１合金经１０ｈ高能球磨转变为弱有序的ｆｃｃ结构，该亚稳态粉末在热压成形过程中发生重有序化转变，恢复至复相结构、成形合金显微组织由Ｌ１２基体和弥散分布的ＤＯ２２结构Ａｌ３（Ｔｉ，Ｎｂ）第二相组成，第二相主要沿基体颗粒周围分布，一部分分布于基体内部，与铸态组织相比，成形合金晶粒明显细化。     

复相Al3Ti基金属间化合物亚稳转变及重有序化

本文研究了Ａｌ６７ＭｎｓＴｉｗ２４Ｎｂ１复相金属间化合物在高能球磨过程中的亚稳态转变及亚稳粉末的加热时重有序化,由Ｌｌ２结构的基体和由ＤＯ２２型Ａｌ３（Ｔｉ,Ｎｂ）第二相组成的Ａｌ６７ＭｎｓＴｉ２４Ｎｂ１复相合金在球磨过程中,Ｌｌ２相有序度下降,ＤＯ２２相溶入,经１５ｈ后合金呈化学无序的ｆｃｃ过饱和固溶体,继续球磨则逐步转为成非晶态,其亚稳转变过程中的结构演变顺序为：Ｌｌ２＋ＤＯ２２→Ｌｌ２（弱有     

Ti3Al基合金中α2／α3＋β相界的计算与测定

对Ｔｉ３Ａｌ－Ｍｏ－Ｎｂ，Ｔｉ３Ａｌ－Ｎｂ－Ｖ，ＴＩ３Ａｌ－Ｚｒ－Ｖ三个赝三元合金系的实验结果表明，α２／α２＋β相界遵守电子浓度规律，且合金元素的电子数由它们的电子结构决定，过渡族Ｔｉ，Ｔｉ，Ｚｒ，Ｖ，Ｍｏ，Ｎｂ的价电子为ｓ＋ｄ电子，即ＮＴｉ＝ＮＺｒ＝４（ｓ＾２ｄ＾２），Ｎｖ＝５（ｓ＾２ｄ＾３），ＮＮｂ＝５（ｓ＾１ｄ＾４）ＮＭｏ＝６（ｓ＾１ｄ＾５）；非过渡族元素Ａｌ的价电子为ｓ＋ｐ电子，即ＮＡｌ     

表面涂少量氯化锰提高Ti47A12Cr2Nb合金高温抗氧化性

研究了表面涂少量ＭｎＣｌ２对Ｔｉ４７Ａｌ２Ｃｒ２Ｎｂ合金９００℃恒温氧化行为的影响,涂少量ＭｎＣｌ２后合金的氧化速率降低了５０％以上,氧化膜也由ＴｉＯ２和Ａｌ２Ｏ３的混合物变为以Ａｌ２Ｏ３为主的氧化物。     

METASTABLE STATE TRANSFOR MATIONS OF Al_3Ti BASE ALLOYS DURING MECHANICAL MILLING AND SUBSEQUENT ANNEALING

１　ＩＮＴＲＯＤＵＣＴＩＯＮＩｔｉｓｃｏｎｓｉｄｅｒｅｄｔｈａｔｔｈｅｂｒｉｔｔｌｅＡｌ３ＴｉｉｎｔｅｒｍｅｔａｌｌｉｃｃｏｍｐｏｕｎｄｃａｎｂｅｄｕｃｔｉｌｉｚｅｄｂｙｃｈａｎｇｉｎｇｉｔｓｔｅｔｒａｇｏｎａｌＤＯ２２ｓｔｒｕｃｔｕｒｅｉｎｔｏｔｈｅｃｕｂｉｃＬ１２ｓｔｒｕｃｔｕｒｅａｎｄｃｏｎｓｉｄｅｒａｂｌｅｓｔｕｄｉｅｓｈａｖｅｂｅｅｎｃｏｎｄｕｃｔｅｄｔｏｄｅｖｅｌｏｐｔｈｅＬ１２Ａｌ３ＴｉａｌｌｏｙｓｂｙａｌｌｏｙｉｎｇｗｉｔｈＦｅ,Ｍｎ,Ｃｒ,ｅｔｃ．Ｈｏｗｅｖｅｒ,ｔｈｅｒ…     

AP-FIM STUDY ON THE MICROSTRUCTURES OF TiAl INTERMETALLIC COMPOUNDS FXBRICATED BY INGOT METALLURGY AND CENTRIFUGAL SPRAY DEPOSITION

1. IntroductionTitanium aluminide alloys based on the ac-TiAl phase are attractive materials for hightemperature structural application. The strength and ductility of two-phase TiAl alloys aremainly decided on microstructural size and morphologiesll32]. The mechanical propertiesof ac--TiAl alloys can be widely changed by microstructural control with millor alloyingand processing. It will be seen that an advanced processing, centrifugal spray deposition(CSD), can offer alloys with a refined…     

添加Nb对LI2型Al3Ti—8Mn基合金的相组成影响

在单相Ll2结构Al67Mn8Ti25金属间化合物中加入少量Nb（0．5at％～4．0at％）,并相应调整Al,Ti含量后,其组织变化显著。在邻近Al－Ti－Nb-8Mn四元系Al3Ti－8Mn区域设计了32种实验合金,随Nb加入量的变化,其结构除单相Ll2外,尚有Ll2＋A12Ti,L12＋DO22,LI2＋LI0,Ll2＋Al2Ti＋DO22和Ll2＋Al2Ti＋Ll0等5种复相或多相组织。Nb含量一定,随Al／Ti比的降低,会导致片状或网纹状Al2Ti组织析出,Nb含量较高时会进一步促使波纹或针片状Ll0TiAl相的形成。初步制定了Al－Ti－Nb-8Mn四元系邻近Al3Ti-8Mn区域的室温相组成图。     

Effects of Nb and Si on high temperature oxidation of TiAl

The isothermal oxidation behavior of TiAl based alloys at 900℃ in air with a combination of Nb (5%-10%, mole fraction) and Si (1%-5%, mole fraction) was investigated. The microstructure and the composition of the oxidation scale were studied by using XRD, TEM and EPMA. The results show that the combination of Nb and Si can improve the oxidation resistance of the alloys significantly. The element Si can change the typical microstructure of oxidation scale on TiAl based alloys. In alloys with Si addition, the compact Al2O3 forms in the interior side of oxidation scale. When x (Si)3%, the Ti5Si3 phase forms and the coarse crystal TiO2 forms on Ti5Si3 phase after oxidation. The increase of Nb content in the TiAl based alloys impedes the growth of Ti5Si3 phase, and the formation of TiO2 on surface and on Ti5Si3 phase is also impeded.     

用正电子湮没技术研究Cr和Nb对TiAl合金中缺陷和d-d电子相互作用的影响

测量Al,Si,Ti,Cr,Nb等纯元素以及Ti50Al50,Ti50l48Cr2,Ti50Al48Nb2合金的符合正电子湮没辐射多普勒展宽谱和寿命谱,获得金属及合金中d电子和缺陷的信息.结果表明,二元TiAl合金的电子密度和3d电子的信号较低,晶界缺陷的开空间较大.在TiAl合金中加入Cr或Nb,合金中的d-d电子作用增强,基体和晶界处的电子密度均增加.Ti50Al48Cr2合金的多普勒展宽谱的d电子信号高于Ti50Al48Nb2合金.讨论了Cr和Nb对TiAl合金中缺陷和d-d电子相互作用的影响.     

Microstructure and tensile properties of orthorhombic Ti–Al–Nb–Ta alloys

Microstructure and tensile properties of orthorhombic Ti–Al–Nb–Ta alloys have been studied. In order to optimize ductility and strength of the orthorhombic alloys with the nominal compositions of Ti–22Al–23Nb–3Ta and Ti–22Al–20Nb–7Ta, various thermomechanical processing steps were implemented as part of the processing route. With a special heat treatment before rolling to obtain a fine and homogeneous rolled microstructure, the rolled microstructure resulted in a good combination of high tensile yield strength and good ductility of the alloys through available solution and age treatments. The duplex microstructure with equiaxed α₂/O particles and fine O phase laths in a B2 matrix, deforming in α₂+B2+O phase field and treating in O+B2 phase field, possesses the highest tensile properties. The R.T. yield strength and ductility of the Ti–22Al–20Nb–7Ta alloy are 1200 MPa, and 9.8% respectively. The yield strength and ductility values of 970 MPa and 14% were also maintained at elevated temperature (650°C).     

TiAl金属间化合物中（Al,Ag）3Ti,Ti3AlC的析出形态

用透射电镜观察了在不同温度，不同时间时效时Ｌｌ０－ＴｉＡｌ金属间化合物中形成的Ｌｌ２－（Ａｌ，Ａｇ０３Ｔｉ，Ｔｉ３ＡｌＣ析出相的形态以及与基体之间的位向关系，讨论了析出相的形态与ＴｉＡｌ基体间的错配度的关系。     

Microstructural Characterization of U-Nb-Zr,U-Mo-Nb,and U-Mo-Ti Alloys via Electron Microscopy

Ternary uranium molybdenum alloys are being examined for use as dispersion and monolithic nuclear fuels in research and test reactors. In this study, three such ternary alloys, with compositions U-10Nb-4Zr, U-8Mo-3Nb, and U-7Mo-3Ti in wt.%, were examined using scanning electron microscopy (SEM), x-ray diffraction (XRD), and transmission electron microscopy (TEM) with high angle annular dark field (HAADF) imaging via scanning transmission electron microscopy (STEM). These alloys were homogenized at 950 °C for 96 h and were expected to be single-phase bcc-γ-U. However, upon examination, it was determined that despite homogenization, each of the alloys contained a small volume fraction precipitate phase. Through SEM and XRD, it was confirmed that the matrix retained the bcc-γ-U phase. TEM specimens were prepared using site-specific focused ion beam (FIB) in situ lift out (INLO) technique to include at least one precipitate from each alloy. By electron diffraction, the precipitate phases for the U-10Nb-4Zr, U-8Mo-3Nb, and U-7Mo-3Ti alloys were identified as bcc-(Nb,Zr), bcc-(Mo,Nb), and bcc-(Mo,Ti) solid solutions, respectively. The composition and phase information collected in this study was then used to construct ternary isotherms for each of these alloys at 950 °C.     

Morphology of L10-TiAl(Ag) precipitation in Ag-modified L12–Al3Ti

Transmission electron microscopy (TEM) examinations of Ag-modified Al₃Ti with an L1₂-ordered structure have revealed the precipitation of L1₀–TiAl upon aging after quenching from higher temperatures. TEM observations revealed that plate-like L1₀–TiAl precipitates lie on {001} planes of (Al,Ag)₃Ti matrix in the short aging period and the habit plane changed from {001} to {hhl} after a long period aging or higher temperature aging and finally to {225} of the matrix lattice. A quantitative X-ray microanalysis for determining the chemical compositions of precipitate and matrix has been done by using an analytical electron microscope. The L1₂ phase field in the Ti–Al–Ag system is severely skewed with respect to the temperature axis and is restricted into a much smaller field at lower temperatures. The coherency stresses across the precipitate/matrix interface is considered to be the main factor controlling the precipitate morphology.     

Microstructure and mechanical behaviour of Nb–Al–V alloys with 10–25 at.% Al and 20–40 at.% V—II: mechanical behaviour and deformation mechanisms

The mechanical behaviour of three Nb–Al–V alloys with nominal compositions Nb–10Al–20V, Nb–15Al–20V and Nb–25Al–40V (in at.%) have been investigated. Both conventional constant strain rate deformation and compressive creep tests have been performed and the deformation microstructures have been examined by transmission electron microscopy (TEM). At room temperature all three alloys deform by planar slip, with dislocation/particle interactions giving significant strengthening for the two phase alloys. Deformation at higher temperatures occurs by a combination of dislocation glide and climb processes, giving more homogeneous microstructures. All of the dislocations in the B2 phase of these alloys are uncoupled superpartial dislocations with b=1/2<111>. The influence of dislocation/domain boundary interactions on the formation of slip bands and uncoupled superpartials is discussed.