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Journal of Materials Science & Technology 2010年第8期26卷 693-704页

作者： R.K.Gupta Bhanu Pant Vijaya Agarwala R.C.Agarwala P.P.Sinha Vikram Sarabhai Space Centre ISROTrivandrum-695 022India Indian Institute of Technology Roorkee

Reaction synthesis process has been used to develop γ titanium aluminide using elemental powders. Powder mixture of Ti-48 at. pct AI was prepared in ball mill and reaction synthesis was carried out in hot press with varying temperature and pressure. titanium aluminide synthesized under high pressure and temperature resulted in better properties with respect to densification, homogenization response, mechanical properties and oxidation resistance as compared to that synthesized under low pressure and temperature. AI rich phases were observed in as-synthesized condition in all the experiments. However, some Ti rich phases were also found in high pressure-temperature synthesized samples. Density, hardness and tensile strength have been correlated with applied pressure through empirical relations. Variation in density with pressure is found to be logarithmic whereas hardness and tensile strength variation with pressure is polynomial.

关键词： titanium aluminide Reaction synthesis Phase transformation

Fractal Dimensions of Hydrogen Induced Brittle Fracture of titanium aluminide

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Journal of Materials Science & Technology 1993年第5期9卷 338-342页

作者： Yue ZHANG Yanbin WANG Lijie QIAO Wuyang CHU Chimei HSIAO Dept.of Materials Physics,University of Science and Technology,Beijing,Beijing,100083,China

The relationship between the stress intensity factor K_1~* required for brittle crack initiation and propa- gation and the fractal dimension D_F of the fracture surface was derived,i.e, InK_1~*=(1/2)In2γE'+(1/2)In(d_f/L_0)(1-D_F) The real surface energy can be calculated based on the measured linear relation of the InK_1~* vs D_F, The equation is not only suitable for the overload fracture but also for the delayed fracture,e.g. hydrogen induced cracking (HIC) and stress corrosion cracking (SCC).The experiment results showed that the hydrogen induced delayed cracking occurred in the Ti-24AI-11 Nb alloy during dy- namic charging,and the threshold stress intensity factor was very low,i.e..K_(IH)/K_(IC)= *** ex- perimental relationship between the stress intensity factor K_1~* and D_F was consistent with the theo- retical equation.

关键词： titanium aluminide hydrogen induced cracking tractal dimension

Effect of niobium alloying level on the oxidation behavior of titanium aluminides at 850°C

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International Journal of Minerals,Metallurgy and Materials 2016年第12期23卷 1452-1457页

作者： Alexandra Banu Maria Marcu Simona Petrescu Nicolae Ionescu Alexandru Paraschiv Faculty of Engineering and Management of Technological Systems Politehnica University of BucharestSplalul Independentei 313060032Bucharest060042Romania Department of Electrochemistry and Corrosion Institute of Physical Chemistry'Ilie Murgulescu'Splaiul Independentei 202Bucharest060021Romania Department of Gas Turbines Special Components COMOTI-R&D Romanian InstituteBd Iuliu Maniu 220061126BucharestRomania

This work addresses the alloying of titanium aluminides used in aircraft engine applications and automobiles. The oxidation resistance behavior of two titanium aluminides of α2 ＋ γ （Ti3Al ＋ TiAl） and orthorhombic Ti2NbAl, recognized as candidates for high-temperature applications, was investigated by exposure of the alloys for 100 h in air. Thus, oxidation resistance was expressed as the mass gain rate, whereas surface aspects were analyzed using scanning electron microscopy in conjunction with energy-dispersive X-ray spectroscopy, and the type of oxidation products was analyzed by X-ray diffraction and Raman spectroscopy. The orthorhombic Ti2NbAl alloy was embrittled, and pores and microcracks were formed as a result of oxygen diffusion through the external oxide layer formed during thermal oxidation for 100 h.

关键词： titanium aluminide thermal oxidation oxidation resistance niobium alloying

A New Process for titanium aluminides Production from TiO_2

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Journal of Materials Science & Technology 2007年第3期23卷 367-372页

作者： A.R.Kamali H.Razavizadeh S.M.M.Hadavi Department of Materials and Metallurgy Engineering IUST University Department of Chemical and Materials Engineering Maleke Ashtar University

This paper describes a new process for producing titanium aluminides, in particular TiAl, from TiO2 raw material. On the basis of obtained results, the non-completed reaction of TiO2 with Al and Ca in a special reaction vessel results in the production of granulates of titanium aluminides especially Ti3Al and other Ti- Al phases as the metallic product and Ca12Al14O33 as the non-metallic product. By adding KClO4 in the mixture, a nearly completed reaction can be carried out. The products of this reaction are titanium aluminide particularly TiAl as the metallic part and CaAl4O7 （grossite） as the non-metallic slag part. Both product and slag are produced in a separated form. This process, called KRH-method is described in this article. The scanning electron microscopic microstructure of metallic part of the product shows different phases： the matrix phase is TiAI, where the needle form precipitation is TiAl2 and the plate form precipitation includes TiAI and Ti3Al phases. The microstructure of the remelted metallic part indicates dendritic phase with a lamellar structure comprising of TiAl and Ti3Al phases. The interdendritic phase of TiAI is also seen.

关键词： titanium aluminide titanium dioxide Grossite KRH process

Twinning and twin intersections inγgrains of Ti-42.9Al-4.6Nb-2Cr

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Journal of Materials Science & Technology 2021年第29期88卷 90-98页

作者： Runrun Xu Miaoquan Li School of Materials Science and Engineering Northwestern Polytechnical UniversityXi'an710072China

A nanoscale observation utilizing the transmission electron microscopy(TEM)device was presented to investigate the hot deformation behavior ofβ-solidifyingγ-TiAl alloy(Ti-42.9 Al-4.6 Nb-2 Cr,at.%)with duplex structure,and elucidate twinning and twin intersections inγ*** showed that twinning is tightly linked to twin intersections inγ*** the initial stage of isothermal compression,faults in two directions with the acute angle of~70°intensively formed inγ*** the proceed of isothermal compression,faults paralleling to each other gradually evolved into twins in the lateral direction,which is helpful to accommodate the atomic plane *** dislocations piled-up advantageously promote longitude twinning inγ*** faults in all directions evolved into twins,various twin intersections phenomena would be observed inγgrains.

关键词： titanium aluminide Thermomechanical processing Twinning Twin intersections

Role of boron in TiAl alloy development: a review

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Rare Metals 2016年第1期35卷 1-14页

作者： Dawei Hu Interdisciplinary Research Centre in Materials University of Birmingham

Boron was found to be a unique grain refiner in cast TiAl alloys in the beginning of 1990 s and has become an element in most of the TiAl alloys developed to *** the past 25 or so years,efforts to understand the role of boron in solidification,solid-phase transformation,thermal and thermomechanical processing and mechanical properties of TiAl alloys and the relevant mechanisms never *** a result,abundant knowledge on boron in TiAl alloys has been accumulated but scattered in various research papers and conference *** review summarises the progress in understanding boron and its impacts on the TiAl alloy systems.

关键词： titanium aluminide TiAl Ti3Al Boron Grain refinement

Solidification characteristics of high Nb-containing γ-TiAl-based alloys with different aluminum contents

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Rare Metals 2015年第6期34卷 381-386页

作者： Yi Liu Rui Hu Hong-Chao Kou Jun Wang Tie-Bang Zhang Jin-Shan Li Ji Zhang The State Key Laboratory of Solidification Processing School of Materials Science and Engineering Northwestern Polytechnical University Institute of High Temperature Materials China Iron and Steel Research Institute Group

The effect of A1 content on the microstructure and solidification characteristics of Ti-A1-Nb-V-Cr alloys in as-cast and isothermally treated states was investigated using X-ray diffraction （XRD）, scanning electron microscopy （SEM） equipped with energy dispersive spectroscope （EDS）, and transmission electron microscopy （TEM）. The typical solidification characteristics are due to the joint influence of both the crystal temperature range and the solidification path. The wide crystallization temperature range contributes to obtaining coarse dendrites in the as-cast Ti47A17Nb2.5V1.0Cr （at%） alloy solidifying through the peritectic reaction. The β-solidifying Ti46A17Nb2.5V1.0Cr （at%） alloy with the narrow crystallization temperature range is attributed to the formation of a homogeneous finegrained microstructure. However, the crystallization temperature range of Ti48A17Nb2.5V1.0Cr （at%） alloy is equivalent to that of Ti46A17Nb2.5V1.0Cr alloy, but it is solidified by peritectic reaction, leading to the formation of finer dendrites.

关键词： titanium aluminide Crystal temperaturerange Peritectic reaction Dendrite morphology Al-equivalent

Processing Maps for Hot Working Behavior of a PM TiAl Alloy

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Journal of Materials Science & Technology 2011年第10期27卷 893-898页

作者： Gang Wang Lei Xu Yong Wang Zhuo Zheng Yuyou Cui Rui Yang Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China

The hot deformation behavior of a Ti-47Al-2Cr-2Nb-0.2W-0.15B （at%） titanium aluminide alloy fabricated by pre-alloyed powder metallurgy has been investigated by using the hot compression tests in the temperature range from 950℃ to 1300℃ and at the strain rates between 10-3 s-1 and 10 s-1. The processing maps have been established to evaluate the optimum hot processing conditions and reveal the instability regions. It is found that the flow stress of the investigated alloy is a strong function of the temperature and the strain rate, The investigated alloy has the optimum hot-working condition at 950℃ and 10-3 s-1, since the material undergoes dynamic recrystallization to produce a fine-grained microstructure. At 1250℃ and 10-3 s-1, the alloy exhibits superplastic deformation. At 2300℃ and 10-1 s-1, the cyclic dynamic recrystallization with high temperature grain coarsening takes place. The material undergoes flow instabilities at lower temperatures and higher strain rates, as predicted by the instability criterion. The processing maps demonstrate that the strain significantly affected the instability regions. The manifestations of the instabilities have been observed in the form of microvoids, wedge cracks, and surface fractures.

关键词： titanium aluminide Powder metallurgy Hot deformation behavior Processing map Dynamic recrystallization

CuTiNiZrV Amorphous Alloy Foils for Vacuum Brazing of TiAl Alloy to 40Cr Steel

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Journal of Materials Science & Technology 2015年第2期31卷 217-222页

作者： Honggang Dong Zhonglin Yang Zengrui Wang Dewei Deng Chuang Dong School of Materials Science and Engineering Dalian University of Technology State Key Laboratory of Advanced Welding and Joining Harbin Institute of Technology Key Lab of Materials Modi fi cation (Dalian University of Technology) Ministry of Education

Vacuum brazing of TiAl alloy to 40Cr steel sheets was conducted with newly developed CuTiNiZrV amorphous foils. It was found that a diffusion layer,filler metal and reaction layer existed in the brazed seam. The diffusion layer in the joint brazed with Cu43.75Ti37.5Ni6.25Zr6.25V6.25(at.%) foil was flat and thin,containing Ti19Al6 and Ti2Cu intermetallic compounds; however,the diffusion layer brazed with Cu37.5Ti25Ni12.5Zr12.5V12.5 foil was uneven with bulges,consisting of essentially Ti-based solute solution. The foil with 12.5 at.% V showed inferior spreadability compared to that with 6.25 at.% V at brazing temperature. However,fracture happened along the diffusion layer with 6.25 at.% V foil due to the formation of brittle intermetallic phases,but the joints brazed with 12.5 at.% V foil failed through the TiAl substrate. These results show that designing amorphous alloy with less Ti and more V for brazing TiAl alloy to steel is appropriate.

关键词： titanium aluminide Steel Dissimilar metal joining

TiAl ALLOYS FOR INDUSTRIAL USE

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Acta Metallurgica Sinica(English Letters) 1995年第Z1期8卷 509-518页

作者： KEIZO HASHIMOTO(Advanced Technologies Research Laboratories Nippon Steel Corp.1618 Ida Nakahara-ku Kawasaki 211 JAPAN) Nippon Steel Corp Kawasaki Japan

Gamma titanium aluminide (γ-TiAl)intermetallic compounds are spotlighted as lightweight heat-resistant materials, and have been investigated extensively to aiming commercial *** approaches in which phase diagrams of Ti -Al -Cr and TiAl -Nb have been studied based on the experimental data and calculations , have been performed in the national project For industrial approach, ingot process and direct casting process have been developed to provide sheet form of TiAl. By these approaches, γ-TiAl base ,intermetallic compounds show a great possibility to apply in the variety of fields .However, a more detailed understanding of phase equilibrium in Ti-Al -X and the relationship between the mechanical properties and microstructure will be necessary

关键词： titanium aluminide PHASE DIAGRAM TENSILE PROPERTY MELTING PROCESS TWIN ROLL CASTING