高强度低密度大模量菲晶态Ai—Li合金

利用单辊快速凝固装置制备出高强度、低密度、大楼量的非晶态Ａｌ６１Ｌｉ２．５Ｙ２５Ｎｉ１１．５（ｗｔ－％）合金，其最大拉伸断裂强度、显微硬度和弹性模量分别为１０３９ＭＰａ、４８８ＤＰＮ和９８．７ＧＰａ．与同成分的晶态合金相比，具有较高的电极电位、较宽的电压钝化区，其腐蚀抗力为晶态合金的７倍．在恒加热速率的晶化过程中出现４个晶化峰，晶化激活能的计算表明，Ａｌ６１Ｌｉ２．５Ｙ２５Ｎｉ１１．５非晶合金的晶化过程为一级反应．     

Morphological and microchemical phenomena in the high-temperature oxidation of binary Al-Li alloys

The high-temperature oxidation behavior of binary Al-Li alloys has been characterized by scanning electron microscopy and secondary ion mass spectrometry in order to understand the mechanism of rapid oxidation in these alloys and to correlate the oxide morphology to its microchemistry. The oxide scale developed on polished specimens during short exposures in air at 530°C shows characteristic nodules that usually nucleate at grain boundaries. Examination of the alloy surface after removal of the oxide layer shows that the initial growth of the oxide nodules occurs laterally in addition to thickening normal to the oxide/alloy interface. Microchemical analysis of the oxide film with a scanning ion microprobe reveals a thick Li-oxide layer at the oxide/gas interface indicating preferential oxidation of Li at the free surface; the rest of the oxide film is composed of both Al- and Li-rich oxides, probably Li₂O and LiAlO₂ The presence of trace impurities (K, Na, F, and Cl) in the oxide scale was also detected. A microstructural model for the development of the oxide film in the Al-Li system is presented on the basis of both morphological and microanalytical data obtained in this study; this new model is compared with existing models.     

Superplastic behavior of Al-Cu-Li based alloy

The superplastic behavior was studied in an Al-4Cu-ILi-0.4Mg-0.4Ag-0.1Zr alloy. The alloys were manufactured both by＂ a conventional rolling route and a thermo-mechanical treatment route. The superplastic properties were evaluated as a function of temperature, strain rate, and processing history. Prior to thermo-mechanical processing, the alloys have elevated-temperature ductilities of 94% to 130%, strain rate sensitivities of about 0.25, and activation energies corresponding to lattice diffusion. After thermo-mechanical processing, the alloys have ductilities of 200% to 630%, strain rate sensitivity of about 0.42, and activation energies corresponding to grain boundary diffusion or a mixture of grain boundary diffusion and lattice diffusion. Skipping rapid recrystallization annealing can supply a higher value of elongation-to-failure.     

铝锂合金焊接技术的研究现状分析

铝锂合金作为轻质金属材料,具有优良的综合性能,因此应用前景十分广阔.从铝锂合金的焊接性出发,分别对铝锂合金弧焊,高能束焊,搅拌摩擦焊,扩散焊以及钎焊的研究现状进行了讨论.结果表明,采用各种焊接技术均可实现铝锂合金的焊接.分析了采用各种焊接技术焊接铝锂合金时的优势以及不足,并对各种焊接技术所获得接头的性能以及工艺改进措施进行了研究.针对目前各种焊接技术急需解决的问题以及铝锂合金焊接的发展方向,总结出了今后铝锂合金焊接研究的重点内容,并对铝锂合金焊接前景进行了分析与展望.     

热处理对1420铝锂合金化学镀镍的影响

对1420铝锂合金进行固溶及固溶后欠时效、峰时效和过时效处理,并对热处理后的试样进行化学镀镍.结果表明,峰时效处理的铝锂合金试样化学镀镍过程容易进行,化学镀镍后在NaCl水溶液中的耐腐蚀性能有所提高.     

Effect of Rare Earth Elements on Anisotropy and Microstructure of AI-Li Alloy 2195 Sheets

For the purpose of decreasing the applied limitation resulting from the anisotropic mechanical property of Al-Li alloy 2195, this study employed a complex heat treatment process, involving the pre-tension, thermo-infiltration of the rare earth element Ce, solution treatment, and artificial aging technology. The results indicate that the infiltration of rare earth element Ce benefits the abatement of anisotropy of Al-Li alloy 2195 sheet, in contrast with that of the normal heat treatment process. The gradient of the Vickers-hardness decreases at least 50% through the thickness, and the tensile strength in the rolling direction also increases significantly. If Ce was infiltrated into the alloy under the optimum pre-deformation, the yield strength （σ0.2） increased by 30 MPa while the tensile strength （σb） enhanced by 25 MPa compared to the rare earth free samples. Meanwhile, the fractography illustrated that the fracture surface of the sample became more desirable.     

2099 Aluminum-Lithium with Key-Locked Inserts for Aerospace Applications

The purpose of this study was to determine the acceptability of nonpenetrating, key-locked inserts in 2099 aluminum-lithium. The tests conducted to make this assessment were: (1) microscopic examination for thread damage and delaminations after key installation, (2) pull-out load at 21 °C (70 °F) and −179 °C (−290 °F), and (3) mechanical cycling tests at room temperature and −179 °C (−290 °F). The test results indicated that for the three sizes evaluated, key-locked inserts in 2099-T6 and 2099-T8 were acceptable and although delaminations did occur on some T6 temper specimens, it was only as a failure mode at ultimate load and such behavior was judged to be acceptable.     

Friction stir welding of aircraft wings

ABSTRACT

To reduce the weight of the wings of the TU-204SM aircraft, investigations were carried out to design the upper wing panel made of the V-1469 high-strength aluminium–lithium alloy of the third generation. The technology of friction stir welding was developed and fragments of the welded panel produced. The tests of the stability under compression showed that the application of the welded panels reduces the weight of the wing by up to ~10% and increases the stability and load carrying capacity by up to ~30%.     

GRAIN BOUNDARY CHARACTER DISTRIBUTION, TEXTURE AND SUPERPLASTIC DEFORMATION BEHAVIOR OF AN AI-Li ALLOY

The grain boundary character distribution and thetexture of 2091 Al-Li alloy recrystallized at different temperatures were measured by TEM and X-ray techniques respectively. The occurrence frequency of low-energy boundaries decreases with increasing recrystallization temperature, while the frequency of highenergy boundaries increases. The strongest component of recrystallization texture in the test temperature range is {011} <111>. The relative intensity of the texture tends to decrease with increasing recrystallization temperature. The material which contains a high frequency of low-energy boundaries exhibits lower deforming stress and high elongation.     

2198-T851铝锂合金激光焊接工艺研究

铝锂合金被认为是在航空航天领域中实现飞行器轻量化的理想结构材料之一。采用高功率光纤激光器焊接1.76mm厚的2198-T851铝锂合金,研究填充ER4047焊丝时激光功率、焊接速率和送丝速率对焊接热裂纹和焊缝组织的影响,以及最优焊接工艺下焊接接头的显微组织与力学性能。结果表明,当激光功率为4kW,焊接速率为4m/min,送丝速率为4m/min时,填充ER4047焊丝焊接可获得成形良好且无宏观裂纹缺陷的焊接接头。接头的平均抗拉强度为342MPa,拉伸断裂后接头断裂强度达到母材的65.4%,熔合区为薄弱部位。