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全片层TiAl基合金的屈服强度与显微组织关系 总被引:4,自引:0,他引:4
通过特定的热处理工艺,分离出全片层组织的晶粒尺度和片层厚度两个主要的显微组织参数,研究了晶粒尺度和片层间距对全片层组织合金的强化效果,研究结果表明:合金的屈服强度随着晶粒尺度和片层厚度的减小而增加,符合Hall-Petch强化关系,同时用屈服强度模型解释了晶粒尺度和片层厚度的强化效果。 相似文献
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以Ti-42.5Al-8Nb-0.2W-0.2B-0.1Y (at. %)合金为研究对象,通过热处理获得不同大小片层团的两种全片层显微组织,并在900 ℃空气条件下,进行了100 h的抗氧化性实验。利用OM、SEM、TEM、XRD和EDS对试样的微观结构、相组成及微区成分进行了分析。恒温氧化动力学结果表明:在900 ℃空气条件下,具有两种不同大小全片层组织的TiAl合金,其恒温氧化动力学曲线符合近抛物线规律,且大片层组织合金的抗氧化性能优于小片层组织。氧化100小时后,大片层组织的合金其氧化增重为7.62 g/m2,小片层次组织的合金的氧化增重为6.45 g/cm2。对合金截面进行观察后发现,大小片层团两种合金表面氧化物的厚度分别为7μm和5μm。通过对氧化动力学曲线、组织结构、氧化膜结构、氧化表面形貌进行综合分析,表明TiAl合金的片层团大小对其氧化行为具有不可忽视的影响。 相似文献
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The stability of lamellar structure is crucial for the creep resistance of TiAl alloys, but degradation of the lamellar structure
is unavoidable at high temperatures. The degradation of the lamellar structure in PST crystals of Ti-48mol.%Al was studied
during high temperature exposure (annealing and creep testing) to examine how to make a stable lamellar structure with high
creep deformation resistance. Since the six orientation variants of γ lamellae are nucleated independently of the adjoining
lamellae, pseudo twin and 120° rotational fault boundaries are most frequently observed at the initial stage of lamellar formation.
The preferential removal of high energy (pseudo twin and 120° rotational fault) boundaries during the evolution of lamellar
structure results in the highly probable appearance of a true twin boundary at a later stage of lamellar evolution. The coarsening
of lamellar spacing and the spheroidization of the lamellae are the major degradation events occurring during creep deformation,
and the migration of the lamellar boundaries brings both of them about. The lamellar structures of TiAl alloy contain four
types of lamellar boundaries. The stability of the four types of boundaries decreases in the following order: γ/α2 > true twin > pseudo twin > or=120° rotational fault boundaries. The γ/α2 boundary has the highest stability (lowest mobility), and the high density of γ/α2 boundaries is proposed to make a stable lamellar structure with good creep resistance. A material having the high density
of γ/α2 boundaries was produced through the heat treatment of a PST crystal in the α+γ two-phase regime. The excellent creep properties
of the material were proven through creep tests of hard oriented PST crystals made of the material.
This article is based on a presentation made in the 2002 Korea-US symposium on the “Phase Transformations of Nano-Materials,”
organized as a special program of the 2002 Annual Meeting of the Korean Institute of Metals and Materials, held at Yonsei
University, Seoul, Korea on October 25–26, 2002. 相似文献
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通过全片层γ-TiAl基合金SEM原位拉伸实验以及对裂纹前方滑移面及解理面上的应用力进行有限元计算,研究了片层界面在形核中的作用,当原裂纹与片层平行时,裂纹尖端滑移秕的分切应力较小,滑移相对困难,片层面上的正应力比其它解理面上的正应力大,从而解理裂纹优先沿片层界面形核;当裂纹与片层界面垂直时,裂纹尖端很多滑移系上的分切应力较大,滑移相对容易,片层面上的正应力远比其它解理面上的正应力小,从而裂纹优等 相似文献
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晶粒尺度和片层厚度对全片层γ—TiAl合金性能的影响 总被引:6,自引:0,他引:6
研究了全片层Ti-46.5Al-2Cr-1.5Nb-1V合金的显微组织与宏观力学性能之间的关系,研究表明,通过不同的热处理制度可以得到具有相同片层厚度的4种晶粒尺度,以及晶粒尺度大约为450um,片层厚度分别为150mm和500nm的组织。材料的屈服强度随着合金晶粒尺度和片层厚度的境加而减小,符合Hall-Patch关系,Ky值为1.82。材料的蠕变抗力随片层厚度的境枷而减小,但是对晶粒尺度的变化 相似文献
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Soo W. Nam H. S. Cho Sun-Keun Hwang Nack J. Kim 《Metals and Materials International》2000,6(4):287-292
Creep deformation behaviors in lamellar TiAl alloys have been investigated. As in the case with metals, the normal primary
creep stage was observed. As creep strain increased within the primary regime, dislocation density decreased, and creep activation
energy increased from 300 kJ/mol, the activation energy of the self-diffusion of Ti in TiAl, to about 380 kJ/mol, that of
steady state creep deformation. During primary creep deformation of lamellar TiAl, as the initial dislocation density decreased,
the α2 -phase was found to transform to a γ-phase, generating new dislocations which contributed to the creep deformation. In other
words, this phase transformation is the source of the dislocation generation for continuous creep deformation. Therefore,
we suggest that phase transformation is the rate controlling processes having an activation energy of about 400 kJ/mol, which
is higher than that of self-diffusion. A small amount of prestrain was found to be responsible for the reduction of initial
dislocation density. In addition, this prestrained specimen showed significantly reduced primary creep strain, and the creep
activation energy in the primary stage was measured to be about 380 kJ/mol. These results clearly confirm the suggested creep
deformation mechanism of lamellar TiAl alloys. 相似文献
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TiO2-coated sericite powders were prepared by the chemical deposition method starting from lamellar sericite and TiCl4 in the presence of La3+. After calcination at 900 ℃ for 1 h, the resultant TiO2 nanoparticles on the sericite surfaces exist in anatase phase. The light scattering indexes of the TiO2-coated lamellar sericite powders are dozens of times higher than those of the naked lamellar sericite powders, varying with different contents of La3+. The presence of La3+ in the deposition solution is beneficial to the formation of the small-sized anatase TiO2 nanoparticles. The presence of La3+ also favors the formation of the dense and uniform island-like TiO2 coating layers in a large range of the mass ratio of TiO2 to sericite from 5% to 20%. XPS analysis shows that when La3+ is absent in the reaction solution, TiO2 coating layers anchor on the sericite surface via Ti-O-Si and Ti-O-Al bonds. The presence of La3+ causes the formation of Si-O-La and Al-O-La bonds on the sericite surface and Ti-O-La bond on the surface of TiO2 coating layers. 相似文献
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MECHANISMSOFα_2→α_2/γPHASETRANSFORMATIONINATiALALLOYXUQiang;LEIChanghui(BeiJingLaboratoryofElectronMicroscopy.ChineseAcademyof... 相似文献
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研究了高压下凝固Ti-48Al合金片层间距及其力学性能的变化。结果表明,压力下凝固时,随着凝固压力的增加扩散系数降低,从而引起片层增厚速度的降低,即片层间距的减小。在常压、2GPa、4GPa下凝固时,片层间距的平均值分别为495,345,227nm。片层组织的显微硬度随着凝固压力的增加而增加。该实验为细化片层间距提供了一种新的方法。 相似文献
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Kyu-Seop Park Dong-Sik Bae Goo-Hyun Lee Sung-Keun Lee 《Metals and Materials International》2005,11(6):481-486
In order to control the spatial Ti−Al distribution of the α2+γ γ lamellar microstructure in Ti−Al alloys, processes consisting of a high-temperature deformation in an alpha single-phase
region, and an annealing and deformation in the α2+γ ψ region were examined. The compression deformation temperatures and strain rates were from 1573 to 1623 K and from 1.0×10−4 to 5.0×10−3 s−1, respectively. Dynamic recrystallization occurred during the compressive deformation in the alpha single-phase region. The
uniaxial compression resulted in the formation of a fiber texture. It was found that more than half of the lamellar microstructure
can be arranged within 30 degrees from the specimen surface by these processes. It was also shown that the orientation control
of the lamellar microstructure in a polycrystalline Ti−Al intermetallic compound is effective in improving the creep resistance
of this material. 相似文献
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Y.G. Zhang J.G. Lin C.Q. Chen Department of Materials Science Engineering Beijing University of Aeronautics Astronautics Beijing China 《中国有色金属学会会刊》1999,(Z1)
1 INTRODUCTIONCreeppropertyofγTiAlalloyisimportanttoitsuseasapotentialhightemperaturematerial.Withoutafundamentalunderstandingofcreepbehavior,thereisagreatriskassociatedwiththeuseofγTiAlintheenvisagedcriticalpropulsionapplications.Sofar,theworkonc… 相似文献
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以Ti-48Al-2Cr-2Nb(at%)合金为研究对象,通过热处理获得近片层和全片层两种显微组织,并在800℃空气条件下,进行了100 h的抗氧化性实验。利用OM、SEM、TEM、XRD和EDS对试样的微观结构、相组成及微区成分进行了分析。恒温氧化动力学结果表明:在800℃空气条件下,对于近片层和全片层两种Ti Al合金组织,其恒温氧化动力学曲线符合近抛物线规律,且近片层组织合金的抗氧化性能优于全片层组织。基于氧化动力学曲线、组织结构、氧化膜结构、氧化表面形貌分析,表明Ti Al合金的片层组织结构对其氧化行为具有不可忽视的影响。 相似文献
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ACOMPONENT-SPECIFICALLOYDESIGNOFTiAlINTERMETALLICSJ.Zhang;D.X.Zou;Z.Z.ZhangandZ.YZhong(CentralIron&SteelResearchInstitute,Bei... 相似文献
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J.N.Wang B.Y.Huang T.G.Nieh National Key Laboratory for Powder Metallurgy Central South University of Technology Changsha China Lawrence Livermore National Laboratory P.O.Box Livermore CA U.S.A. 《中国有色金属学会会刊》1999,(Z1)
1 INTRODUCTIONTiAlalloyshaveattractedagreatdealofresearchinterestbecauseoftheirpotentialapplicationsinaerospaceandautomobileindustries.Thelargestproportionofusageofthesealloysisinaircraftgasturbines,forexample,asturbineblades.Insuchapplication,cree… 相似文献
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采用标准试样,测试了全层片组织Ti33Al3Cr0.5Mo(质量分数,%,下同)合金的室温断裂韧性(以下简称断裂韧性)。在SEM、TEM下原位观察了板状和薄膜状合金试样中裂纹产生及扩展的动态过程。发现试样的断裂韧性因层片板条取向的不同而呈现各向异性,α2相层片板条对裂纹的扩展具有阻碍作用并使裂尖发生钝化。基于以上原因,使得层片板条取向呈现随机性的合金试样具有高的室温断裂韧性。 相似文献