通过关键词查论文: Al-Cu-Li Alloy

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作者: Ji Fa Zhong, Zi Qiao Zheng, Xian Fu Luo
摘要: In this work, a new ultra-high strength Al-Cu-Li alloy was investigated. The ultimate strength, yield strength and elongation of the newly designed alloy by artificial aging are 647.2MPa, 609.4MPa and 7.3% respectively. Among the main strengthening phases of T1, θ′ and S′ in the experimental alloys, T1 is the dominant one. The combined addition of Mg and Ag promoted the precipitation of T1 and increased the strength of the new alloy greatly. Zn had a similar effect as Ag during the aging strengthening progress, when added with Mg. Among the three micro-alloying elements, Mg, Ag and Zn, Mg had the strongest influence on age strengthening. Compared with the combined additions of (Mg +Ag) and (Mg + Zn), (Ag + Zn) had the weakest influence on aging strengthening. Pre-deformation before aging promoted the precipitation of T1 phase which weakened the influence of micro-alloying elements (Mg, Ag and Zn) on strengthening the alloys and minished the strength difference between alloy containing (Mg + Ag + Zn) and alloys containing two of them.
1050
作者: Ye Rim Lee, Hyun Ho Jung, Jong Hoon Yoon, Joon Tae Yoo, Kyung Ju Min, Ho Sung Lee
摘要: Aluminum-Copper-Lithium alloys are used as substitute for conventional aerospace Al alloys in cryogenic tank of liquid rocket engines, aircraft wing box and satellite systems due to their high specific modulus and specific strength. For this reason they are currently under consideration for one of the potential choices for a large structure of Korea Space Launch Vehicle. In this study, friction stir welding and electron beam welding were conducted on AA2195 sheets, in butt joint configuration in order to compare the two processes and to evaluate mechanical properties. The results provide valuable information for the optimal condition of joining AA2195 sheets for a large tankage structure of the space launcher.
178
作者: Hyun Ho Jung, Ye Rim Lee, Kyung Ju Min, Ho Sung Lee
摘要: Aluminum-Copper-Lithium alloys are of strategic important [1] in lightweight aerospace structures due to their high specific modulus and specific strength and are under consideration for one of the potential choices for Korea Space Launch Vehicle structure. However, this is one of the most complicated alloys due to the precipitation of a large number of second phase particles. In this study, the precipitation kinetics of an Al-4.3%Cu-1.2%Li alloy was studied by differential scanning calorimetry (DSC) technique since precipitation plays an important role for hardening of this alloy. Several models including Kissinger’s, Starink’s and Chaturvedi’s were used to obtain the activation energy and precipitation kinetics.
3
作者: Li Fan, Wen Ke Han
摘要: The competitive precipitation behavior between T1 and σ phases in Al-Cu-Li alloy was studied by hardness test, XRD and TEM observation. The hardness test results show that the changing curves are related to the densities of vacancies and dislocations, and competitive precipitation between age hardening precipitates. T1 phases give rise to the rapid age hardening. XRD results indicates that there exists an alternation increase in peak value of diffraction intensity ranged from 40 to 45° of the aged alloy for various ageing time. About four precipitation sequences occur during ageing of Al-Cu-Li alloy, including δ', θ, T1 and σ sequences. Competitive kinetics between T1 and σ phases result in the phenomenon of different precipitation behavior.
106
作者: Jesús Lugo-Quintal, Luis Díaz-Ballote, Lucien Veleva, Antonio Contreras-Cuevas
摘要: The corrosion behavior in NaCl solutions at different pH values of Al-Cu-Li/SiCp and Al-Cu/SiCp composites fabricated by co-spraying technique was studied. The corrosion behavior of the composites was also compared with the corrosion behavior of pure aluminum. Corrosion potential measurements and potentiodynamic polarization were used to elucidate the corrosion behavior of the composites. In addition the microstructure and morphology of the composites were studied through X-ray diffraction (XRD) and scanning electron microscope (SEM). It was found that the corrosion rate of Al-Cu-Li/SiCp and Al-Cu/SiCp composites was higher than corrosion rate of pure aluminum for all NaCl solutions tested. Both composites and pure aluminum showed the typical “U” behavior of the corrosion rate as a function of pH. The addition of lithium had little effect on the corrosion behavior of the composites.
133
作者: Yue Wu, Xu Dong Wang, Jiong Li Li, Zhao Hui Feng
摘要: The microstructure evolution during homogenization of 2A66 Al-Cu-Li alloy was investigated by optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDX), transmission electron microscopy (TEM) and differential scanning calorimeter (DSC). The results showed that the dendritic segregation can be found in the ingot of experimental alloy. Numerous eutectic phases can be observed in the grain boundary, and the distribution of the main elements along the interdendritic region varied asymmetrically. It was found that the main secondary phase was Al2Cu. Differential scanning calorimeter (DSC) results showed that the over-burnt temperature of 2A66 Al-Cu-Li alloy was 515°C. With the increase of homogenization temperature in the area of 480°C~510°C, the boundaries of experimental alloy became sharp and the most of secondary phase dissolved into the matrix. The experimental alloy heat treated at 520°C was over-burnt. The Al3Zr precipitated and α (Al) super-lattice was observed by TEM in the experimental alloy after homogenization.
575
作者: Yue Wu, Xu Dong Wang, Jiong Li Li, Zhao Hui Feng
摘要: The effect of solution temperature on the solid solubility, microstructure and mechanical properties of 2A66 Al-Cu-Li alloy was studied by optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and tensile test. The results show that with the solution temperature increasing from 480°C to 520°C,the amount of residual phases decreased and the solid solubility increased obviously, while the recrystallization hardly changed with the increasing of solution temperature. With the solution temperature increased to above 530°C, the amount of residual phases almost did not change. With the solution temperature increasing to above 540°C, the alloy was over-burnt obviously. Complete dissolution of the particles in the 2A66 Al-Cu-Li alloy was obtained after solution treatment at 520°C.
687
作者: Ye Rim Lee, Kookil No, Jong Hoon Yoon, Joon Tae Yoo, Ho Sung Lee
摘要: It is well known that the addition of Li to aluminum alloys offers an attractive combination of low density and high modulus, which are useful for lightweight structures of aerospace vehicles. However, microstructure of Al-Li alloys are complex, which consist of a number of equilibrium and metastable phases. In addition, Al-Li alloys are weldable but the weldability is not as good as that of other aerospace alloys. This is due to the reactive property of element Li during melting and causes porosity, cracking and low joint efficiency. In friction stir welding (FSW), rotating welding tool generates frictional heat and by keeping the tool rotating and moving speed, the heat from friction causes the plate to soften without melting. Therefore, this solid state welding is adequate to Al-Li alloys. The friction stir welded joint was divided into 9 regions and each microstructure was investigated in detail to present the microstructure evolution and material flows during friction stir welding process. The recrystallized structure is observed in nugget zone and the evidence of initiation of dynamic recrystallization is found around the boundary between thermo-mechanically affected zone (TMAZ) and nugget region. This paper describes the results of a study to investigate the microstructure change of Al-Cu-Li alloy during the friction stir welding process.
240
作者: Niraj Nayan, S.V.S. Narayana Murty, S.C. Sharma, K. Sreekumar, Parameshwar Prasad Sinha
摘要: In the present study, thermal treatments for homogenizing cast structures of Al-Cu-Li alloy AA2195 for improved workability are developed chiefly by empirical methods and detailed Differential Scanning Calorimetry (DSC) and microstructural characterization. DSC has been carried out on as-cast samples to establish the homogenization temperatures and avoid incipient melting. Homogenization time has been calculated empirically and microstructural characterization and DSC has been carriedout to after each cycle to validate the empirically established homogenization cycle. Homogenization cycle (435°C/8hrs+495°C/12hrs+525°C/32hrs) has been established for AA2195 alloy having an average grain size of 500μm based on calorimetric studies and microstructural examination.
557
作者: Niraj Nayan, S.V.S. Narayana Murty, S.C. Sharma, K. Sreekumar, Parameshwar Prasad Sinha
摘要: A novel technique of pure Lithium addition has been adopted for the processing of Al-Cu-Li alloy AA2195 cast ingots (7-8 kg each) in VIM under dynamic inert atmosphere, which gives more than 95% recovery of Lithium. The cast billets were homogenized, forged and converted into 12mm diameter rods by caliber rolling in the temperature range of 250°C, 300°C, 350°C and 400°C. The caliber rolled rods were treated to T8 (Solution Treatment+WQ+CW+Aging) condition. Mechanical properties were evaluated for T8 tempered bars at room temperature and correlated with microstructural observations. Highest mechanical properties in T87 temper have been obtained for rods caliber rolled at 350°C temperature.
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