Preparation and Corrosion Resistance of Rare Earth Ceramic Film on AZ91 Magnesium Alloy

With the purpose of improving corrosion resistance and solving environmental pollution caused by traditional protective technique, rare earth ceramic film on AZ91 magnesium alloy was prepared by dip coating process, and technical parameters of preparation were defmed. Microstructure and composition of the film were studied and corrosion resistance was evaluated as well. The results show that rare earth ceramic film is uniform,dense, with strong cohesion and intact coverage. The film is mainly made up of CeO2 and MgCeO3. The results of corrosion experiments approve that the film acts as a barrier to isolate the contact of the substrate with corrosion media and decreas corrosion rate. Polarization curve of the coated sample shiftes to positive potential obvito 2.7 × 104 Ω. These facts indicate that rare earth ceramic film could effectively improve corrosion resistance of AZ91 magnesium alloy.     

Preparation and Performance of Rare Earths Chemical Conversion Film on Magnesium Alloy

Golden yellow cerium conversion film was obtained on magnesium alloys surface by immersion method and the preparation parameters were established. The influence of different process parameters on the surface morphology and performance of the conversion film were analyzed by means of SEM and electrochemical method. Formation dynamics about cerium conversion film on magnesium alloy in solution containing cerium salt and the anti-corrosion behavior of the conversion film in 3.5% NaCl solution were studied by electrochemical method respectively. The results shows that the conversion film is more compact at room temperature when concentration of cerium sulfate is 10 g·L-1 in the solution; the open circuit potential of the magnesium sample moves up to positive direction about 100 mV, the surface of conversion film becomes even and lustrous, and the adhesion intensity of conversion film increases when adding aluminum nitrate into the solution containing cerium salt. The pH value of the solution and immersion time of the sample in the solution also affect the surface morphology and anti-corrosion property of the conversion film. After covered by rare earths conversion film, the anti-corrosion property of magnesium alloy is obviously improved. Rare earth conversion film has self-repairing capability in corrosion medium.     

Improving Corrosion Resistance of Cf/Mg Composites using Rare Earth Conversion Coatings

The surface of carbon fiber reinforced Mg matrix (Cf/Mg) composites was modified by treatment of rare earth conversion coating, and nontoxic, non-pollution Ce conversion coatings were prepared. The effect of the coatings on corrosion behaviors of composites was investigated by electrochemical polarization technology and electrochemical impedance spectroscopy (EIS) in 3.5% NaCl solution. The higher Ecorr and lower icorr were obtained by Ce conversion coatings. EIS results showed that the higher values of R2 were obtained by treatment containing CeCl3, the high corrosion resistance occured in treatment containing CeCl3, the low corrosion resistance in uncoating sample, the coating of treatment containing Ce(NO3)3 was medium. The microstructure of Ce conversion coatings was observed by scanning electron microscopy (SEM), and the elements of corresponding for coatings was characterized by energy dispersive spectrometer (EDS). The micro-cracks and Ce-riched spherical particles were characteristics of these coatings.     

Influence of Cerium on Corrosion of AZ91 Magnesium Alloy

Effect of cerium addition on corrosion resistance of AZ91 magnesium alloy was investigated using the static weight loss and polarization curve method as well as metallographical observation. The results indicate that a small amount of cerium （0.2% - 0.8%） in AZ91 magnesium alloy can significantly reduce the corrosion rate, enhance the electrode voltage and lower corrosion current density in 3.5%NaCl aqueous solution, and AZ91-0.8% Ce alloy has better corrosion resistant performance. The reason for increasing corrosion resistance is attributed to the addition of Ce, refining the α-Mg grain, reducing the segregation of element Al, and improving the morphologies of β-Mg17 Al12 phases.     

Structure and Corrosion Resistance of Microarc Oxidation Coatings on AZ91D Magnesium Alloy

Magnesium alloys are widely used as shells of 3C (computer, mobile phone and consumer electronics) equipments for its impressive mechanical and physical properties, such as low density, good resistance to electromagnetic radiation, suitable for high pressure diecasting and easily recycling, etc. But poor corrosion resistance confines its extensively application. In this paper, protective coatings was successfully prepared on AZ91D magnesium alloys by micro-arc oxidation (MAO) and painting process. Microstructures and phases of MAO coatings were invesgated with scanning electron microscope (SEM) and X-Ray diffractometer. Mechanical properties of MAO coating, such as adhesive force and corrosion resistance, were also tested. Results showed that MAO coatings were a good base for painting process. MAO coatings with paint have good adhesive properties to base metal and excellent corrosion resistance. Micro-arc oxidation with painting process is a good kind of surface treatment to improve the corrosion resistance of mobile phone shell made of AZ91D magnesium alloys.     

Study on Ignition Proof AZ91D Magnesium Alloy Chips with Cerium Addition

The effect of Ce on ignition point of AZ91D magnesium alloy chips was studied. For the AZ91D and the AZ91D-xCe magnesium alloys, changing the sizes of the chips in the range of 58 - 270 μm has a limited influence on ignition point, however, the shift of the content of Ce has much effect on ignition point. Increasing the Ce content, x from 0.15 to 0.25, the ignition point increases with increasing of Ce; however, x from 0.25 to 0.45, the ignition point decreases with increasing of Ce. By the addition of Ce of 0.25 %. the ignition point is raised by 43℃.     

稀土镁合金的研究进展

从防氧化、除氢、合金流动性、细化品粒与强化作用等方面概括稀土元素在镁合金中的作用，综述稀土镁中间合金，铸造、变形稀土镁合金与快速凝固稀土镁合金的最新研究动向与成果，并简介发展非品镁合金与镁合金的超塑性研究的巨大潜力。     

稀土对铁基自熔合金喷焊层组织与耐蚀性能的影响

通过熔炼—雾化工艺制备了稀土铁基自熔合金粉末,并考察了稀土对铁基自熔合金喷焊层的显微组织及其在弱酸、中性盐溶液中耐蚀性能的影响。采用金相显微镜、SEM、EDAX对合金喷焊层的物相结构、显微组织进行了观察和分析。在实验结果的基础上,对稀土的有关作用机制进行了分析和讨论。     

稀土在耐热镁合金中的应用

本文介绍了稀土对耐热镁合金发展的影响 ,概括了稀土耐热镁合金的发展历史及现状。初步讨论了稀土元素对镁合金耐热性能的影响机理。对稀土耐热镁合金的研制开发、应用前景进行了展望。     

稀土铁基自熔基合金抗硫化氢腐蚀性能的实验研究

近年来关于稀土在热喷涂（焊）材料中的应用研究正日益受到人们的重视。铁基自熔合金末作为一种广泛使用的热喷涂（焊）材料具有价格低廉，喷涂（焊）层的耐磨性较好等优点，但其耐蚀性较差。为此，本研究引入稀土对其改性。通过熔炼－雾化工艺制备了稀土铁基自熔合金粉末，并考察了稀土对铁基自熔合金喷焊层在硫化氢介质中气蚀和在含硫化氢的中性氯化钠溶液中浸蚀的影响。结果表明，铁基自熔合金（含稀土和不含稀土）喷焊层试样表现出较强的抗硫化氢能力。铁基合金喷焊层试样在含硫化氢的4Wt%NaCl溶液中的腐蚀速率随稀土的添加量增加量增加而逐渐降低，且稀土添加量有最佳值0.2Wt%。     

稀土元素在铝合金转化膜中的应用

铝合金稀土转化膜具有优异的耐蚀性能和无毒无污染等优点,是最具希望代替铬酸盐有毒处理、有良好发展前景的转化膜之一.本文从成膜工艺、膜的组成、结构及形貌、成膜机理和耐蚀机理四个方面介绍了铝合金稀土转化膜技术在国内外的研究进展及现状,展示了稀土元素在铝合金转化膜中广阔的应用前景,并对这一技术未来的发展方向提出了展望.     

金属表面稀土转化膜的研究进展

本文介绍了稀土转化膜工艺在提高不锈钢、镁合金、铝合金等材料表面耐蚀性能中的应用 ,综述了国内外在此研究领域的最新进展 ,结合作者目前从事的研究工作 ,从理论上阐明了稀土转化膜工艺的成膜机制与耐蚀机理。     

正脉冲电压对Mg-4Gd-3Y-0.5Zr合金微弧氧化膜组织形貌与耐蚀性能的影响

采用SEM、覆层测厚仪、电化学工作站等研究了正脉冲电压对Mg-4Gd-3Y-0.5Zr稀土镁合金双脉冲微弧氧化膜的组织形貌及耐蚀性能的影响。结果表明：随正脉冲电压的升高,膜层厚度增加,膜层表面微孔数量减少、孔径增大,烧结强度增加,裂纹增大;耐蚀性能先增强后降低,均显著优于合金基体;最佳正脉冲电压为450 V,腐蚀电位与腐蚀电流分别为-1.495 V、10-8.62 A/cm2。     

Effect of ErCl3 Addition on Microstructures and Properties of AZ91 Magnesium Alloy

Effect of ErCl_3 Addition on Microstructures and Properties of AZ91 Magnesium Alloy     

稀土和铬对铁基自熔合金涂层耐蚀性的影响

本研究着眼于考察稀土和合金成分对铁基自熔合金涂层的耐蚀性的影响,对不同成分的合金涂层进行了三酸一盐的浸蚀试验。结果表明在硫酸和硝酸溶液中,稀土的添加对合金涂层的耐蚀性有利,但在盐酸和氯化钠溶液中,稀土的添加对合金涂层耐蚀性无益。铬含量高的铁基自熔合金涂层在硝酸溶液中有优良的耐蚀性,但在硫酸和盐酸中的耐蚀性不如铬含量低的铁基自熔合金涂层。文中分析了不同合金在试验中的不同表现的原因,进而为铁基自熔合金的进一步工业应用提供有用的信息。     

Mechanism of Effects of Rare Earths on Microstructure and Properties at Elevated Temperatures of AZ91 Magnesium Alloy

By using real-space recursion method,the energetics of the undoped and Al and/or RE atoms doped 7（1450）〈0001〉 symmetric tilt grain boundaries（GBs）in AZ91 alloys were investigated.Similar calculations were performed on undoped and doped bulk α Mg for comparison.The results showed that Al atoms segregated at GBs in AZ91 alloys.When RE atoms were added,they also segregated at GBs,and their segregation is stronger than Al atoms＇.Therefore,RE atoms retard the segregation of Al atoms.Calculations of interaction energy indicated that Al atoms repelled each other,and could form ordered phase with host Mg atoms.On the contrary to the case of Al,RE atoms attracted each other,they could not form ordered phase with Mg,but could form clusters.Between RE and Al,there existed attractive interaction,and this attractive interaction was the origin of Al11RE3 precipitation.Precipitation of Al11RE3 particles with high melting point and high thermal stability along GB improves high temperature properties of AZ91 alloys.     

Study on Y-Base Rare Earth Alloy in Ultra-High Hardfacing

The effect of Y-base rare earth alloy in ultra-high hardfacing was observed by means of OM, SEM and XRD. Precipitated carbide can be metamorphosed and spheroidized in surfacing by adding Y-base rare earth alloy, which contributes to the increase of precipitated carbide. Rare earth combined with oxygen and sulfur can improve the morphology of slag inclusion as well as purify surfacing. The result shows proper rare earth alloy in surfacing can fine its microstmcture, improve hardness and impact toughness.     

Effects of RE on Microstructures and Mechanical Properties of Hot-Extruded AZ31 Magnesium Alloy

Effects of rare earth (RE) additions on microstructure and mechanical properties of the wrought AZ31 magnesium alloy were investigated. The results show that, by adding 0.3%, 0.6% and 1.0% RE elements, the as-cast microstructure can be refined, and the as-cast alloys‘ elongation and tensile strength can be improved. After extrusion, the alloy with 0.3 % and 0.6% RE additions obtain a finer microstructure and the best mechanical properties, but the alloy with 1.0% RE addition has the coarse A1-RE compound particles in grain boundaries which decreased elongation and tensile properties. Usually, Rare earth (RE) elements were used to improve the creep properties of aluminium-containing magnesium pressure die cast alloys at elevated temperatures. In this paper, it is also found that the high temperature strength of extruded materials can be increased by RE elements additions.     

稀土元素Nd对铸造镁合金组织和性能的影响

综述了稀土元素Nd对不同铸造镁合金组织以及力学性能影响的研究概况;分析了Nd在多种铸造镁合金中的作用,稀土对镁合金具有净化、细化、合金化等作用,可产生细晶、固溶、时效沉淀和弥散等强化;展望了稀土元素在铸造镁合金中的研究与应用前景。     

稀土镁硅铁合金中的氧化镁夹杂物

本文论述了稀土镁硅铁合金中主要非金属夹杂物—氧化镁的生成原因及其对应用的危害 ,提出了降低合金中氧化镁的方法。