共查询到20条相似文献,搜索用时 62 毫秒
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运用XD工艺制备了颗粒增强TiAl基复合材料。增强颗粒均匀分布于TiAl基体中并细化TiAl合金。通过在TiB_2/TiAl、TiC/TiAl复合材料中加入适量的Si,颗粒增强TiAl基复合材料的室温延性得到了改善。 相似文献
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TiAl基合金中的不连续粗化转变 总被引:4,自引:0,他引:4
为细化铸造TiAl基合金的显微组织,将成分为Ti-44.9Al、Ti-48Al以及Ti-44.3Al-3.0Cr(at%)的三种合金在略高于Ti-Al共析温度的1150℃进行长时保温处理。结果表明,保温一定时间后,合金中的Ti3Al+TiAl片层组织会发生三种类型的不连续粗化转变,转变结果均能在一定程度上细化合金的铸态晶粒尺寸,其中Ti-44.3Al-3.0Cr合金的晶粒细化效果最佳。此外,Al含量的增加,合金元素Cr的加入等都会大大促进合金的不连续经转变过程。 相似文献
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金属基复合材料的熔体直接反应合成工艺 总被引:10,自引:0,他引:10
介绍了一种新型金属基复合材料制备工艺-熔体直接反应合成工艺,重点介绍了Al3Ti/Al、TiB/Al、TiC/Al颗粒增强复合材料制备工艺及其性能。 相似文献
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研究了涂层对Ti纤维及Ti纤维强化γ-TiAl金属间化合物基复合材料性能的影响。研究结果表明,运用物理气相沉积法(PVD)在Ti纤维表面涂覆Y2O3制得Ti/TiAl复合材料,不仅改善了γ-TiAl及其复合材料的力学性能,而且使纤维与基体间的界面反应层厚度减小,涂覆Y2O3较Al2O3有较高的稳定性,这对深入研究涂层对复合材料合成及性能的影响有着重要的意义。 相似文献
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自生TiC增强钛基复合材料的微观组织 总被引:6,自引:0,他引:6
采用反应自生法制备了TiC颗粒增强钛合金基复合材料,研究了复合材料的相组成和微观组织。在Ti-6Al-2C合金中存在Ti和TiC两种相。TiC权树枝状初生Tic和短棒状共晶TiC两种开头存在,其中共晶TiC主要存在于晶界,特别是三角晶界处。TiC晶格常数的计算结果表明TiC的衍射峰存在一定的偏移,主要是由于存在于TiC中的C空位引起晶格畸变。随着Al含量的增加,初生TiC由发达粗大的树枝晶变为不发达的树枝晶,当Al含量为35%时变为短棒状和薄片状的TiC。基体组织也相应地由单一的Ti基体变为Ti和Ti3Al的两相基体以及Ti3Al和TiAl两相基体。根据相图分析了组织变化的主要原因。 相似文献
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本文采用粉末冶金法制制备了含Ti的SiCp/2024Al复合材料。研究表明,在复合材料制备工艺条件下,部分Ti与Al反应形成了Al3Ti,粗大的Al3Ti/Ti复合颗粒的存在降低了复合材料的室温拉伸强度和塑性,但可以提高屈服强度和弹性模量。 相似文献
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研究了Al含量和C/Ti对Al+Ti+C复合系热爆反应合成Al/TiC的反应过程及生成相组成的影响。实验结果表明:随着Al含量的增加,反应温度降低,反应时间延长,但反应起始温度几乎没有变化;C/Ti对反应温度和反应时间有很大的影响,但对反应起始温度影响很小。在对生成相组成的研究中发现:当C/Ti=1.25、Al含量不大于60at%和C/Ti=1、Al含量不大于50at%时,生成物只有TiC;随着Al含量的增加,生成Al_3Ti的量增加,并通过热力学理论对反应合成自由能进行了计算,计算结果与试验结果相吻合。另外,通过扫描电子显微镜(SEM)对生成的TiC的组织形貌进行了观察。结果表明:生成的TiC尺寸均匀,约为0.3~0.8μm,大多数呈球状,部分为块状。 相似文献
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Al+Ti+C复合系热爆反应合成过程及相组成研究EI 总被引:1,自引:1,他引:0
研究了Al含量和C/Ti对Al+Ti+C复合系热爆反应合成Al/TiC的反应过程及生成相组成的影响。实验结果表明:随着Al含量的增加,反应温度降低,反应时间延长,但反应起始温度几乎没有变化;C/Ti对反应温度和反应时间有很大的影响,但对反应起始温度影响很小。在对生成相组成的研究中发现:当C/Ti=1.25、Al含量不大于60at%和C/Ti=1、Al含量不大于50at%时,生成物只有TiC;随着Al含量的增加,生成Al_3Ti的量增加,并通过热力学理论对反应合成自由能进行了计算,计算结果与试验结果相吻合。另外,通过扫描电子显微镜(SEM)对生成的TiC的组织形貌进行了观察。结果表明:生成的TiC尺寸均匀,约为0.3~0.8μm,大多数呈球状,部分为块状。 相似文献
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研究了不同环境气氛对成分为Ti-46Al-2Cr-0.2Si-0.1Nd(at%)的TiAl基合金室温塑性的影响。结果表明该合金在室温下对环境脆性是敏感的,在不同气氛中的拉伸塑性依次为O2〉Air(空气)〉H2〉Ar+H2O。水汽和氢气均引起环境脆性,但水汽比氢气更有害。 相似文献
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M. Prez-Bravo M. L. N I. Madariaga K. Ostolaza J. San Juan 《Materials Science and Engineering: A》2004,370(1-2):240-245
In order to study the microscopic mechanisms controlling the plastic deformation at high temperature of two γ-TiAl alloys with nominal compositions: Ti–46.5Al–4(Cr, Nb, Ta, B) and Ti–45Al–(5–10)Nb (in at.%), internal friction (IF) measurements have been performed. A subresonant torsion pendulum has been used working in two different modes; changing the temperature between 300 and 1200 K at a constant frequency, and varying the frequency between 0.001 and 10 Hz at a fixed temperature. The resulting mechanical spectra show an anelastic relaxation peak at about 1060 K at 1 Hz in one of the alloys and a high-temperature background in both of them. Activation parameters of the loss peak have been calculated and an activation enthalpy of about 3.8 eV is obtained. The characteristics and a possible responsible mechanism for this relaxation peak are discussed. 相似文献
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This paper studies the chemical interaction on contact, and the related evolution of composition and microstructure of cast TiAl-based alloy, when using refractory oxygen-free pyrolytic boron nitride (pBN) crucibles/moulds instead of traditional oxide ceramic ones. We extend the research begun with AlN crucibles and reported in [4]. Three melting tests were performed in resistive SiC electro-furnace with Ti–46Al–8Nb (at%) alloy in 6N-purity pBN boat crucibles with fixed melt superheating times of 5, 12 and 25 min at 1670 °C and subsequent quenching with high-purity Ar gas flow. As-cast samples were examined by optical microscopy/metallography, X-ray diffractometry, SEM-BSE, EDX and EBSD micro-analyses, and compared to the initial material. Unlike the AlN it was shown that dissolved BN reacts with the melt, forming Ti2AlN and (Ti,Nb)B micro-precipitates at the expense of selective destruction of the α2-Ti3Al major intermetallic phase in the solidified alloy: Ti3Al + (Nb) + BN → Ti2AlN + (Ti,Nb)B. The key features and temporal dynamics of this interaction are studied. 相似文献
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Honggang Dong Lianzhen Yu Dewei Deng Wenlong Zhou Chuang Dong 《Materials and Manufacturing Processes》2015,30(9):1104-1108
The effect of post-weld heat treatment (PWHT) on the mechanical properties and microstructure of direct friction-welded joint between TiAl alloy and 42CrMo steel rods was investigated in this paper. It was found that solid joint between TiAl alloy and 42CrMo steel could be obtained without adding interlayer. After PWHT at 580°C for 2 h, the tensile strength of the joint reached 405 MPa, and fracture happened through the TiAl alloy substrate with quasi-cleavage features. The tempered sorbite formed near the interface, improving the joint strength significantly. It was found that TiFe2, TiAl, and small amount of TiC brittle phases formed at the interface, and the interfacial layer was as thin as 2–5 µm. The precipitated phases were 1 µm in average size, and distributed discontinuously at the interface. 相似文献
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TiAl intermetallics and Ti3AlC2 ceramics were jointed through diffusion bonding using Ti/Ni interlayer. The effect of bonding temperature and holding time on interfacial microstructure and mechanical properties of the bonded joints were investigated. The typical interfacial microstructure of the joint from TiAl to Ti3AlC2 side could be divided into τ3-Al3NiTi2, α2-Ti3Al, α-Ti + δ-Ti2Ni, δ-Ti2Ni, β2-TiNi, η-TiNi3, γ-(Ni)ss, γ′-Ni3(Al, Ti), γ′-Ni3(Al, Ti) + Ti3AlC2, respectively. The value of the microhardness in the reactive zones increased due to the formation of intermetallcs. Lower or higher bonding temperature and longer or shorter holding time both resulted in low strength owing to the insufficient diffusion of atoms or excessive formation of intermetallics. A high bonding strength can be obtained when bonding at 920 °C for 60 min. Fracture occurred through the intermetallic layer adjacent to the Ti3AlC2 substrate during shear test, showing brittle intergranular and transgranular characteristic. 相似文献
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High Nb containing TiAl porous alloys were synthesised by powder metallurgy (PM). In order to reveal reaction mechanism of Nb in preparation of the porous alloys, Nb–Al diffusion reaction was investigated using diffusion couples at relatively low temperatures of 600–800°C. The porous Nb–Al diffusion layer was identified as NbAl3 phase and the thickness of diffusion layer indicated that the Nb–Al diffusion mainly occurred at 800°C. In addition, the pore diameter distribution indicated that Nb–Al diffusion also contributed to the increase in pore diameter. According to these results, the diffusion reaction model was established for high Nb containing TiAl porous alloys. 相似文献
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Jiancheng Tang Baiyun HuangYuehui He Wensheng LiuKechao Zhou Aihua Wu 《Materials Research Bulletin》2002,37(7):1315-1321
The dependences of the room temperature tensile properties of two-phase TiAl alloys with fully lamellar microstructures on colony size and the effects of alloying elements on the k value of Hall-Petch relationship were investigated. It is found that the ultimate tensile strength and the yield strength show Hall-Petch dependences on colony size, but the ductility does not obey a Hall-Petch dependence on colony size. The k value of Hall-Petch relationship increases when Ti-47Al (at.%) is alloyed with interstitial elements C or B, but the additions of substitutional elements Cr or Nb don’t lead to its apparent change. 相似文献
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Superplastic behavior of a TiAl alloy was investigated in a temperature range between 800 and 1000°C and at a strain rate of 1×10−4 s−1. The results show that the present alloy possesses very good superplasticity even in its as-cast state. A tensile elongation of 628% was obtained at 850°C. The observed superplastic behavior can be explained by the formation of a fine microstructure containing a metastable β-phase during solidification. 相似文献