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在18%(质量分数,下同)H_2SO_4+5%C_2H_2O_4水溶液中,采用脉冲(PC)电流对2198和5A90两种铝锂合金进行阳极氧化处理。用扫描电子显微镜(SEM)观察铝锂合金阳极氧化膜表面和截面形貌;用能谱仪(EDS)对其成分进行面扫描和线扫描;用动电位极曲线检测氧化膜在3.5%NaCl水溶液中的耐蚀性。结果表明:2198和5A90铝锂合金阳极氧化膜主要由Al的氧化物组成;2198合金氧化膜表面存在细小颗粒,厚度约为150μm;5A90合金氧化膜表面存在微孔,为后续封孔处理提供结构条件,厚度约为180μm;用脉冲方法在两种铝锂合金表面生成的较厚阳极氧化膜具有较高的耐蚀性。 相似文献
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用失重法和电化学方法研究2A12,5A06和7A04铝合金在中性和酸性(pH≈5)连续盐雾环境下的腐蚀过程。通过金相显微镜和接触角表面分析仪观察其金属相界面处的腐蚀形貌和表面状态,分析腐蚀机理。结果表明:失重法、极化曲线Tafel外推法和电化学阻抗谱法均显示3种铝合金在中性盐雾中腐蚀速率的大小关系为7A042A125A06;在酸性盐雾中腐蚀速率的大小关系为7A045A062A12;铝合金表面与中性和酸性盐溶液的接触角分别为70.9°和52.6°,酸性盐溶液的接触角小于中性盐溶液的接触角,可能是因为氢离子增多使阴极反应右移,加速阳极溶解,破坏了铝合金表面的氧化膜。 相似文献
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《中国航空学报》2019,32(11):2516-2525
The stress corrosion cracking (SCC) susceptibility of 2297 Al-Li alloy in 1 M NaCl + 0.01 M H2O2 solution (CP solution) and 1 M NaCl + 0.01 M H2O2 + 0.6 M Na2SO4 solution (CPS solution) was investigated by slow-strain rate tests at various strain rates ranging from 10−5 s−1 to 10−7 s−1. The roles of H2O2 and SO42− in the corrosion process were estimated by potentiodynamic polarization and electrochemical impedance spectroscopy. 2297 Al-Li alloy does not fracture ascribed to SCC in CP solution, while it undergoes SCC in CPS solution. In CPS solution, with a decreasing strain rate from 10−5 s−1 to 10−7 s−1, the SCC susceptibility firstly rises and then declines exhibiting a peak value at a strain rate of 10−6 s−1. H2O2 promotes the active dissolution while SO42− lowers the corrosion rate. The SCC fracture is associated with a decline in the dissolution rate of the crack tip by SO42−, which leads to stress concentration. In CPS solution, a reduction in the local dissolution rate of the crack tip leads to stress concentration, resulting in SCC fracture. As the preferred initiation site for a crack, pits also show a noteworthy effect on SCC of 2297 Al-Li alloy. 相似文献
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The present work examines the effects of cerium salts on corrosion behaviors of Si–Zr hybrid sol–gel coatings. The Si–Zr hybrid sol–gel coatings on a 2A12 aluminum substrate were prepared through hydrolysis and condensation of glycidoxypropyl-trimethoxy-silane(GTMS) and zirconium(IV) n-propoxide(TPOZ). Used as inhibitors for corrosion, three types of cerium salts(Ce(NO_3)_3, CeCl_3, and Ce(CH_3COO)_3) were doped into the sol–gel coatings. Fourier transform infrared(FTIR) and scanning electron microscopy(SEM) were employed to investigate the structures and morphologies of various coatings, and the corrosion resistances of the coatings were evaluated by electrochemical methods and neutral salt spray tests. Experimental results indicate that the addition of cerium salts can hinder the process of corrosion due to their self-healing abilities. Furthermore, the sol–gel coating doped with Ce(CH_3COO)_3 has the best corrosion resistance because of the promotions of hydrolysis and condensation provided by CH_3COO. 相似文献
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To evaluate stress corrosion cracking(SCC) mechanism of low alloy ultra-high strength steel 30CrMnSiNi2 A in environment containing NaCl, SCC behavior of the steel in 3.5wt% NaCl solution is investigated by slow strain rate technique(SSRT) with various strain rates and applied potentials, surface analysis technique, and electrochemical measurements. SCC susceptibility of the steel increases rapidly with strain rate decreasing from 1 · 10 5s 1to 5 · 10 7s 1, and becomes stable when strain rate is lower than 5 · 10 7s 1. SCC propagation of the steel in the solution at open circuit potential(OCP) needs sufficient hydrogen which is supplied at a certain strain rate.Fracture surface at OCP has similar characteristics with that at cathodic polarization 1000 mVSCE, which presents characteristic fractography of hydrogen induced cracking(HIC).All of these indicate that SCC behavior of the steel in the solution at OCP is mainly controlled by HIC rather than anodic dissolution(AD). 相似文献
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Effects of RRA Treatments on Microstructures and Properties of a New High-strength Aluminum-Lithium Alloy-2A97 总被引:1,自引:0,他引:1
YUAN Zhi-shan LU Zheng XIE You-hua DAI Sheng-long LIU Chang-sheng 《中国航空学报》2007,20(2):187-192
A new high strength 2A97 Al-Cu-Li-X alloy was subjected to triple-aging of retrogression and re-aging treatments (RRA). Transmission electron microscopy (TEM), differential scanning calorimetry (DSC), and tensile tests were used to investigate the effects of RRA treatment on the microstructures and properties. DSC test reveals the reversion temperature range of the strengthening δ' (Al3Li)phase. The results show that the microstructure consists of δ' (Al3Li) phase, T1 (Al2CuLi) phase and θ"/θ'(Al2Cu) phase for 2A97 alloy treated by a triple-aging ora retrogression and re-aging treatment in the following order: (1) at 165 ℃×30 min, (2) at 220 ℃ or 240 ℃×15 min, (3) at 165 ℃×24 h. The plastic deformation, incorporated into the treatment after secondary high temperature aging, promotes the T1 precipitation during final re-aging. The tensile properties of the alloy treated by the retrogression and re-aging treatment reach the peak level of alloy single-aged at 165 ℃ in T6 temper. 相似文献
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交流阻抗谱法评价热障涂层的热腐蚀行为(英文) 总被引:1,自引:0,他引:1
本文利用交流阻抗这种无损检测的方法研究了热障涂层在质量分数为25%NaCl+75%Na2SO4混合盐体系中的热腐蚀行为。实验结果显示,热腐蚀条件下,在陶瓷层和粘结层界面处形成TGO层为混合氧化物层,成分为Cr2O3、(Ni,Co)(Cr,Al)2O4和NiO,其厚度增长符合抛物线规律。热障涂层在110个循环腐蚀之前时,TGO层的电阻值随其厚度的增加而增加;110个循环后,虽然TGO层的厚度还是在增加,但由于TGO层孔隙的增多而导致其电阻值有所下降。陶瓷层的电阻值随着陶瓷层中裂纹的萌生和扩展而不断增大。等效电路中得到的参数可以用来表征热障涂层的失效行为。 相似文献
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《中国航空学报》2021,34(5):183-194
Electrochemical trepanning (ET) is one of the main methods for processing the blisks in aero-engines. However, stray corrosion in ET has a very negative impact on the machining quality of the blades. This paper proposes an innovative ET method with an auxiliary electrode surrounding the inner wall of the cavity above the cathode. Two-dimensional electric-field models are established and simulations are carried out with the auxiliary electrode at different positions and different electric potentials. The electric-field simulations show that adding the auxiliary electrode reverses the directions of the current lines in the processed area, thereby protecting it. The results show that when the distance from the bottom of the auxiliary electrode to the top of the cathode tool is 3 mm and the potential difference between the auxiliary electrode and the anode workpiece is 5 V, the area corroded by stray current is decreased. Experiments are performed under the parameter values determined by the simulations, and they confirm that this method is effective at reducing stray corrosion. Specifically, at a feed rate of 2.5 mm/min, the blade taper angle is decreased from 1.37° to −0.09°, the thickness of the leading and trailing edges is increased from 0.307 mm to 0.704 mm, and the average surface roughness is decreased from Sa =8.239 μm to Sa=7.028 μm. 相似文献
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纯镁和镁锂合金在中性3.5%NaCl溶液中的腐蚀行为 总被引:2,自引:0,他引:2
采用电化学方法研究了纯Mg和Mg-Li合金在中性3.5%NaCl溶液中的腐蚀行为,采用扫描电镜观察了腐蚀后的表面形貌,利用XRD测试了腐蚀前后纯Mg和Mg-Li合金表面的组成成分,并用失重法测试了腐蚀速率。结果表明:腐蚀初期,纯Mg的腐蚀电流小于Mg-Li合金,纯Mg的腐蚀电位高于Mg-Li合金,纯Mg的电化学反应电阻大于Mg-Li合金。经过24h腐蚀后,纯Mg的腐蚀速率大于Mg-Li合金,且两者腐蚀形貌不同,纯Mg的腐蚀坑大而深,蚀坑数量少;Mg-Li合金的腐蚀坑小而浅,蚀坑数量多并且表面变黑。纯Mg的腐蚀产物主要为Mg(OH)2,Mg-Li合金的腐蚀产物主要为Mg(OH)2,LiOH,MgLi,Mg3Li7,Al2O3。 相似文献
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In order to investigate the yielding behavior of the newly developed Ni 3 Al-based intermetallic alloy IC10, yield stresses have been measured in tension and compression with different orientations. The specimens were cut from a sheet with different angles inclined from the solidification direction. The inclined angles were taken to be 0 , 22.5 , 45 , 67.5 and 90 . All experiments were conducted at room temperature except for orientation 0 , whose deformation temperatures ranged from 298 to 1273 K. Experimental results show that the yield strength of alloy IC10 has the anomalous behavior which has been observed for other Ll 2 -long-range ordered intermetallic alloys, but it is less pronounced. The abnormalities show the following characteristics: (i) the yield strength increases as the temperature is raised below the peak temperature, (ii) yield strength anisotropy, (iii) tension/compression asymmetry. Compared to Ni 3 Al single crystals, the polycrystalline exhibits some different yielding behaviors which may be due to the high volume fraction of c phase. 相似文献
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Degradation of thermal barrier coatings (TBCs) caused by calcium-magnesium-alumina-silica (CMAS) glassy penetration is becoming an urgent issue for TBCs industrial applications. In this work, yttrium aluminum garnet (Y3Al5O12, YAG) nano-powders were synthesized through a chemical co-precipitation route. The resistance of YAG ceramic to glassy CMAS infiltration at 1250?°C was evaluated. YAG ceramic bulk sintered at 1700?°C for 10?h was comprised of a single garnet-type Y3Al5O12 phase. The molten CMAS glass was suppressed on the surface of the YAG ceramic at 1250?°C. A chemical reaction between YAG and the molten CMAS glass did not occur at 1250?°C for 24?h, suggesting that YAG could act as an impermeable material against glassy CMAS deposits in the TBC field. 相似文献
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《中国航空学报》2021,34(4):451-464
For higher efficiency and precision manufacturing, more and more attentions are focused on the surface roughness and residual stress of machined parts to obtain a good fatigue life. At present, the in-situ TiB2/7050Al metal matrix composites are widely researched due to its attractive properties such as low density, good wear resistance and improved strength. It is of great significance to investigate the machined surface roughness, residual stress and fatigue life for higher efficiency and precision manufacturing of this new kind material. In this study, the surface roughness including two-dimensional and three-dimensional roughness, residual stress and fatigue life of milling in-situ TiB2/7050Al metal matrix composites were analyzed. It was found from comparative investigation that the three-dimensional surface roughness would be more appropriate to represent the machined surface profile of milling particle reinforced metal matrix composites. The cutting temperature played a great role on the residual stress. However, the effect of increasing cutting force could slow down the transformation from compressive stress to tensile stress under 270 °C. An exponential relationship between three-dimensional roughness and fatigue life was established and the main fracture mechanism was brittle fracture with observation of obvious shellfish veins, river pattern veins and wave shaped veins in fracture surface. 相似文献
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《中国航空学报》2019,32(8):1994-1999
An environmental barrier coating (EBC) consisting of a silicon bond coat and an Yb2SiO5 top-coat was sprayed on a carbon fibers reinforced SiC ceramic matrix composite (CMC) by atmospheric plasma spray (APS). The microstructure of the coating annealed at 1300 °C and its high-temperature oxidation behavior at 1350 °C were investigated. The significant mass loss of silica during the plasma spray process led to the formation of Yb2SiO5 and Yb2O3 binary phases in the top-coat. Eutectics of Yb2SiO5 and Yb2O3 were precipitated in the top-coat, and channel cracks were formed in the top-coat after 20 h annealing because of the mismatch between the coefficients of thermal expansion (CTEs) of Yb2SiO5 and the SiC substrate. The EBC effectively improved the oxidation resistance of the CMC substrate. The channel cracks in the Yb2SiO5 top-coat provided inward diffusion channels for oxygen and led to the formation of oxidation delamination cracks in the bond coat, finally resulting in spallation failure of the coating after 80 h oxidation. 相似文献