2198和5A90铝锂合金脉冲阳极氧化膜制备及耐蚀性

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。     

航空用铝合金在酸性盐雾环境中腐蚀电化学

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。     

SCC evaluation of a 2297 Al-Li alloy rolled plate using the slow-strain rate technique

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.     

Effects of cerium salts on corrosion behaviors of Si–Zr hybrid sol–gel coatings

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.     

快速凝固Mg-5Zn-1Y-0.6Zr合金腐蚀性能的研究

研究了快速凝固Mg-5Zn-1Y-0．6Zr合金在3．5％NaCl溶液中的腐蚀行为。利用金相显微镜、SEM观察了合金的微观组织和腐蚀形貌。结果表明,快速凝固使合金产生非晶相、晶粒细化及微观组织均匀,均对耐腐蚀性能提高起到作用。在室温下,腐蚀速率随时间先增大,随后逐渐减小。XRD分析表明腐蚀后的主要产物是Mg（OH）2。通过极化曲线测试,表明合金耐蚀性能随冷却速率的提高而改善。     

SCC investigation of low alloy ultra-high strength steel 30CrMnSiNi2A in 3.5wt%NaCl solution by slow strain rate technique

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).     

5A05铝合金黑色氧化膜的结构及耐蚀性能

用两步化学氧化法在铝合金表面获得了黑色氧化膜。利用全浸渍腐蚀试验及电化学极化曲线评价了膜的耐蚀性能,利用扫描电子显微镜观察膜的表面形貌,采用能量散射谱(EDS)测定膜的成分。结果表明:铝合金的黑色氧化膜具有网块状结构,膜层主要由O、Al、Mn、Co、Cr五种元素所组成,未经封闭的铝合金氧化膜的耐蚀性能很差,而经重铬酸钾封闭后,耐蚀性大为提高。     

Effects of RRA Treatments on Microstructures and Properties of a New High-strength Aluminum-Lithium Alloy-2A97

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.     

交流阻抗谱法评价热障涂层的热腐蚀行为(英文)

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。     

Electrochemical trepanning with an auxiliary electrode

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 S_a =8.239 μm to S_a=7.028 μm.     

乙酸钴的掺杂对LY12铝合金表面溶胶凝胶膜层耐蚀性的影响

在LY12铝合金表面制备了防护性溶胶凝胶膜层,并研究了乙酸钴的掺杂对膜层耐蚀性能的影响.采用扫描电子显微镜(SEM)和电子能谱(EDS)分别观测溶胶凝胶膜层的微观结构和成分.采用电化学方法研究了乙酸钴浓度对溶胶膜层在浸泡实验中耐蚀性的影响;通过观察人为缺陷处在0.05 mol/L NaCl腐蚀溶液中形貌、成分的变化,对...     

推进剂贮箱用2A14铝合金接头应力腐蚀性能研究

为了研究推进剂贮箱用2A14铝合金接头介质相容性,分析了铝合金的应力腐蚀机理,以2A14-T6铝合金本体、搅拌摩擦焊(FSW)接头和变极性氩弧焊(VPTIG)接头为研究对象,通过慢应变速率拉伸法进行应力腐蚀试验研究。结果表明,2A14铝合金在3.5%NaCl溶液中存在应力腐蚀现象,FSW接头的抗腐蚀性能优于VPTIG接头。。     

纯镁和镁锂合金在中性3.5%NaCl溶液中的腐蚀行为

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。     

Yield anisotropy and tension/compression asymmetry of a Ni3Al based intermetallic alloy

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.     

新型超高强度钢应力腐蚀断裂行为研究

采用恒载荷拉伸应力腐蚀实验研究了23Co14Ni12Cr3及40CrNi2Si2MoVA两种超高强度钢在质量分数为3.5％的NaCl溶液中的应力腐蚀开裂行为,为两种超高强度钢在结构件中的安全使用提供数据依据.通过金相显微镜和扫描电镜(SEM)对两种超高强度钢的显微组织以及断口形貌进行了分析.恒载荷拉伸应力腐蚀实验结果表...     

Impermeability of Y3Al5O12 ceramic against molten glassy calcium-magnesium-alumina-silicate

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.     

Ni47Ti44Nb9形状记忆合金耐蚀性能和抗氧化性能研究

采用高温氧化、电化学腐蚀测试,并结合SEM,XRD等分析手段,研究了Ni47Ti44Nb9合金的氧化性能和抗腐蚀性能。结果表明,Ni47Ti44Nb9合金在450℃下氧化非常轻微,600～800℃下合金的氧化增重曲线近似符合抛物线规律。经高温氧化后,合金表面形成的氧化层具有分层结构,氧化截面由外氧化层和过渡层组成。电化学腐蚀结果表明,溶液中NaCl含量越低,溶液温度越低,合金的腐蚀电流密度越小,腐蚀电位正移,保护膜的稳定性提高。     

Investigation on surface roughness,residual stress and fatigue property of milling in-situ TiB2/7050Al metal matrix composites

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.     

Microstructure and high-temperature oxidation behavior of plasma-sprayed Si/Yb2SiO5 environmental barrier coatings

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.     

波形和频率对GC-4钢腐蚀疲劳裂纹扩展特性的影响

对三角波、正锯齿波、负锯齿波、方波和负脉冲波5种波形及3种频率为1Hz、5Hz、20Hz对GC-4(40CrMnSiMoVA)钢在3.5％NaCl中性溶液中疲劳裂纹扩展速率的影响进行了试验研究。结果表明,GC-4钢腐蚀疲劳(CF)具有显著的波形和频率效应;在CF过程中可同时存在静态应力腐蚀(SSCC)和动态应力腐蚀(DSCC),DSCC可以在K_(max)相似文献