Leng CHEN
,
Weimin MAO
,
Yongning YU
,
Huiping FENG
材料科学技术（英文）
An X-ray diffractometer that equipped with a two-dimensional detector is used for developing the technique of grain size measurement for strong textured and coarse-grained Si steel sheet. The method is based on the concept that the position of diffraction spots depends on the orientation of individual grains. The two-dimensional detector has the ability to collect abundant diffraction information in seconds, thus it can be determined rapidly and accurately whether a series of diffraction spots come from the same grain. The experimental results show that this method can be used for measuring grain size and its distribution in strong textured and coarse-grained metal sheets.
关键词:
Grain size
,
null
,
null
Jingbo SONG
,
Weimin MAO
材料科学技术（英文）
The effect of trace Sn on the pitting morphology of high voltage anode aluminum foils was investigated. The distributions of microelement Sn, Fe, Si, Cu and Mg in the surface layer of aluminum foils with different Sn content were determined by using a secondary ion mass spectrometer. It was found that the micro-alloyed Sn is enriched at the external surface. The mechanism of pitting behavior of trace Sn on aluminum surface is similar with that of lead. Enrichment of Sn in the surface layer provides large numbers of sites for initiation of pitting corrosion, while pitting sites appeared relatively inhomogenously in the foils without Sn. Sn, as an eco-friendly microelement, can be applied to replace Pb in improving the homogenous pitting behaviors of high voltage aluminum foils, in which the volume fraction of cube texture is not reduced.
关键词:
Electrolytic capacitor
,
铝箔
,
锡
,
孔腐蚀
Guohui ZHU
,
Weimin MAO
,
Yongning YU
材料科学技术（英文）
The orientation distribution of recrystallization grains formed during annealing, as well as their misorientation relationship to the deformation matrix in cold rolled FeCo alloy have been investigated. It was found that most of the recrystallization nuclei were located near the boundary area with rather random orientations, and their misorientation angles to the deformation matrix were generally very high. However a few nuclei were also observed inside the deformation grains, to which they had very similar orientations. Therefore the misorientation angles between the nuclei and the deformation matrix were generally very low. The orientation and the misorientation distributions of the nuclei have very strong influence on the recrystallization process which could result in a very weak recrystallization texture. The corresponding mechanism is discussed.
关键词:
Applied Surface Science
A novel kind of micro-arc oxidation (MAO) coating was prepared on magnesium alloy surface coated with rare earth conversion film (RE-film) in an alkaline aluminum oxidation electrolyte by AC power source. Inspection of scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared (FTIR) microspectroscopy, the structure and composition of MAO coating formed on AZ91D with RE-film under different applied voltages were investigated and the performance of the optimized MAO coating compared with the MAO coating directly formed on magnesium alloy. As the pretreatment of magnesium alloy with RE-film, the cerium oxides can be incorporated into the MAO coatings, reduce porosity of the MAO coating surface and enhance the thickness of MAO coating. These structure features and the cerium oxides incorporated into the MAO coating result in greatly improved corrosion resistance. Base on electrochemistry impedance spectroscopy (EIS) measurement, the electronic structure and composition analysis of the MAO coating, a double-layer structure, with a compact inner layer and a porous outer layer, of the coating was proposed for understanding its corrosion process. (C) 2010 Elsevier B.V. All rights reserved.
关键词:
Magnesium alloy;Rare earth conversion film;Micro-arc oxidation;Porosity;az31 magnesium alloys;micro-arc oxidation;mg-al alloys;electrolyte;resistance;cerium;phosphate
Science China-Technological Sciences
Product/metal ratio (PMR) was introduced as a novel criterion for the evaluation of electrolytes on micro-arc oxidation (MAO) of Mg and its alloys. The criterion initially sprang from Pilling-Bedworth ratio (PBR), focused on the roles of electrolytes for the compactness of the fabricated coatings, and took attention on properties of reactants/products during MAO. Meanwhile, based on our experiments as well as the results from literatures, the effects of electrolyte additives on morphologies and compositions of the fabricated MAO coatings of Mg alloys were exploited for verification and supplement of the initial criterion. In combination of the initial PMR criterion and experimental verification, PMR could be represented by special mode (PMR (s)=V (oxide products)/V (alloy substrates)) and general mode (PMR (g)= PMR (s)+ PMR (d)). The ideal PMR (s) should be between 1 and 2, while PMR (d) is related to the coating deposition during MAO. PMR (d) is a supplement to PMR (s) when the effect of the overlaying property (O) of the coatings and the effective deposition (D) of electrolyte composites are considered (PMR (d)=f(O, D). O is related to the melting point (MP) and boiling point (BP) of the MAO products. D is related to the effective reactions between alloy substrates and electrolytes during MAO.
关键词:
micro-arc oxidation;Mg alloys;Pilling-Bedworth ratio;product/metal;ratio;az91d magnesium alloy;electrochemical corrosion behavior;silicate-containing electrolytes;ceramic coatings;potassium fluoride;resistance;films;surface;microstructure;technology
Electrochimica Acta
Protective composite coatings were prepared on magnesium alloy AZ91D by micro-arc oxidation (MAO) treatment plus a top coating with sealing agent using multi-immersion technique under low-pressure conditions. The corrosion resistance of AZ91D alloy with composite coatings was superior evidently to that with merely MAO film. SEM observations revealed that the sealing agent was integrated with MAO film by physically interlocking; therewith covered uniformly the surface as well as penetrated into pores and rnicro-cracks of MAO film. The anti-corrosion properties in 3.5% NaCl solution of the composite coatings were evaluated by using electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization measurements. Based on the results of chronopotentiometric (E similar to t) and EIS measurements for long time immersion in 3.5% NaCl solution, appropriate equivalent circuits for the composite coatings system were proposed. It follows that due to the blocking effect of the sealing agent in pores and cracks in MAO film, the composite coatings can suppress the corrosion process by holding back the transfer or diffusion of electrolyte and corrosion products between the composite coatings and solution during immersion. (c) 2005 Elsevier Ltd. All rights reserved.
关键词:
composite coatings;MAO film;sealing;magnesium alloy AZ91D;EIS;micro-arc oxidation;impedance spectroscopy;interfacial factors;phosphate coatings;alkaline-solutions;aluminum-alloys;nacl solution;anodic films;mg alloys;part 2
Materials and Corrosion-Werkstoffe Und Korrosion
A rapid and convenient anodization technology with AC power source to obtain the MAO films formed on magnesium alloy AZ91D in phosphate bath (base electrolyte + Na3PO4) with or without aluminate and silicate was studied. The corrosion resistance of the anodic films was studied by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization techniques and the microstructure and composition of films were examined by SEM and XRD. The results show that Na3PO4 can promote the occurrence of sparking during the MAO process, while abundant heat generated by sparking might enhance the formation of the glassy phase of the compound when the electrolyte contains the additives of NaAlO2 and Na2SiO3 simultaneously. The optimized MAO film is ivory-white smooth by naked eye, while presents porous and microcracks in microscopic scale. The anodic film formed in the alkaline solution with optimized parameters possesses superior corrosion resistance by electrochemical test. The XRD pattern shows that the components of the anodized film consist of MgO, MgAlO2, and MgSiO3. No oxide crystal with P element can be found.
关键词:
micro-arc oxidation;electrochemical impedance spectroscopy;koh-aluminate solutions;corrosion protection;ceramic coatings;alloys;anodization;parameters;resistance;behavior
杨巍
,
汪爱英
,
柯培玲
,
代伟
,
张学谦
材料工程
doi:10.3969/j.issn.1001-4381.2012.04.019
采用线性离子束沉积技术于AZ80镁合金微弧氧化(MAO)陶瓷层表面沉积不同厚度的类金刚石碳(DLC)膜,形成DLC/MAO复合膜层.对比研究4种膜基系统的表面结构特征、力学性能以及摩擦学性能差异.结果表明:随DLC膜厚度增加,复合膜层表面微孔数量减少,孔径减小,但凹凸不平趋势增加,且DLC膜表面颗粒特征更加明显,表现为DLC-80min/MAO/AZ80膜基系统具有最小的表面粗糙度,最大的硬度H、弹性模量E及H/E值；不同厚度DLC/MAO/AZ80膜基系统平均摩擦因数较MAO/AZ80显著降低；DLC膜厚度增加导致3种复合膜基系统的表面微观结构改变,使得摩擦因数与磨痕形貌存在差异；各膜基系统表面磨痕处均形成了Fe的转移层,由于表层DLC膜“裸露”的大量C对磨损界面具有很好的润滑作用,而使得镁合金基体获得有效保护.
关键词:
镁合金
,
微弧氧化
,
类金刚石碳膜
,
微观结构
,
性能
刘永明
,
贺晓慧
,
陈义旺
,
伍青
催化学报
采用双-(β-酮萘胺)镍(Ⅱ)为主催化剂,以甲基铝氧烷(MAO)为助催化剂,在甲苯溶剂中进行了苯乙烯聚合实验,并考察了聚合温度、Al/Ni摩尔比、单体浓度和聚合时间等因素对聚合反应的影响. 结果表明,双-(β-酮萘胺)镍(Ⅱ)/MAO催化剂显示出很高的催化活性,可催化苯乙烯聚合得到中等分子量和分子量分布较窄(Mw/Mn＜1.6)的聚苯乙烯. 采用核磁共振氢谱、核磁共振碳谱、傅里叶变换红外光谱、差示扫描量热法和广角X射线衍射技术对聚合产物进行了表征. 结果表明,所得聚合物为无规聚苯乙烯.
关键词:
镍
,
络合物
,
后过渡金属催化剂
,
苯乙烯
,
聚合
,
聚苯乙烯
