镁合金研究开发现状与展望

介绍了镁合金研究开发和应用领域的国内外发展动态,耐热镁合金、耐蚀镁合金、高强高韧镁合金、变形镁合金等高性能镁合金材料的最新发展,镁合金压铸、半固态铸造、挤压铸造、超塑性、冲锻等成形技术的最新开发研究成果,指出了镁合金研究开发的发展趋势,提出了我国在镁和镁合金研究开发和应用领域需要注意的问题。     

稀土对镁合金微弧氧化层的作用综述

镁合金具有密度小、比强度高、可回收、优异的铸造性能和切削加工性能等特点,在航空航天、交通工具、3C产品等领域具有十分广泛的应用前景。然而,镁合金的耐蚀耐磨性能差,限制了其更广泛应用。采用微弧氧化技术处理镁合金表面,来提高镁合金的耐蚀耐磨性能是近几年新兴的表面技术。在微弧氧化过程中,镁合金表面不断地陶瓷化,最终获得与镁合金基体结合紧密的致密耐蚀耐磨陶瓷层。本文介绍了镁合金微弧氧化反应原理,综述了稀土对镁合金微弧氧化层作用形式,包括前处理、作为添加剂添加在电解液中以及稀土合金化方式。探讨了稀土对镁合金微弧氧化层的影响作用,稀土通过影响微弧氧化过程、改变微弧氧化层的形貌和提高耐蚀相比例来改善微弧氧化层的耐磨耐蚀性能。指出今后可能的研究方向,通过选择电导率合适、降低Mg O熔点和粘度的稀土盐添加剂,从而提高微弧氧化膜层的致密性和耐蚀相比例,有利于镁合金微弧氧化层性能的改善。     

镁合金的工艺特性及挤压过程工艺参数的确定与举例分析

在简略介绍镁及镁合金的工艺特性的基础上,详细论述了镁及镁合金的挤压工艺特点及其与铝合金挤压的主要区别,例举了大量的镁及镁合金热挤压工艺的参数实例,对研制镁合金挤压新产品有一定参考价值。     

纯镁及镁合金强流脉冲电子束处理微观组织分析

研究了纯镁及镁合金强流脉冲电子束处理后微观组织的变化，改性层呈现特殊的层状结构，最表层为50～100nm的纳米氧化镁，下面是6～10μm的重熔层，重熔层下面是热影响区和应力波作用区，其中产生孪晶变形，提出了强流脉冲电子束处理纯镁及镁合金改性层的结构模型，并对其形成机制进行了初步分析。     

推进再生镁规范发展

随着镁合金应用技术的不断提高,镁及镁合金在各个行业的用量日益增大,废镁和废旧镁合金的回收与利用产生了巨大的需求空间,镁合金的循环利用具有重要意义,已经成为突出课题。镁合金的熔化潜热比铝合金低得多,比铝合金消耗的能量少,因而镁及其合金是易于回收的金属,目前使用的镁合金均可以回收。一方面是回收失效或报废的镁合金零部件,另一方面是回收镁在生产过程中的废料和切屑。     

镁合金加工工业及技术的发展特点与趋势

本文简略地介绍了轻合金的特点及应用领域,重点论述了镁及镁合金的特性与用途,镁及镁合金材料产业的生产与技术发展历史、现状与趋势,重点分析了我国镁及镁合金产业的发展现状与水平,并指出了发展方向与前景。我国已是世界镁业大国,正在向镁业强国进军。     

镁及镁合金等通道转角挤压研究进展及发展趋势

镁及镁合金属于HCP结构,织构和晶粒尺寸是影响其性能的主要因素.本文对近年来镁及镁合金等通道转角挤压(Equal channel angular pressing,ECAP)的研究状况进行了综述,介绍了ECAP过程中影响镁及镁合金织构的主要因素.根据晶粒细化机制的不同,从两方面介绍了ECAP工艺制备镁及镁合金超细晶、纳...     

镁合金的发展趋势

本文概述了镁合金产业的动向和镁合金技术新进展。指出了镁合金向着高强度、耐热、阻燃、耐蚀、抗变形发展及其在交通、车辆、3C产品中的应用前景。     

镁及镁合金的应用与研究

介绍了我国镁资源的分布情况、国内外金属镁的生产情况、镁及镁合金的分类,分析了镁合金的特点及其在不同领域的应用情况,以及我国镁合金的研究现状.     

稀土镁合金研究现状与发展趋势

概述了镁合金的特点及其应用发展状况,分析了稀土镁合金元素的作用机理及性能改善,讨论了用稀土合金元素制备高性能(耐热、耐蚀、阻燃及高力学性能)镁合金的基础作用.展示了发展高性能稀土镁合金的优势和意义,展望了稀土镁合金的发展趋势.     

Dispersion strengthened aluminum-4 pct magnesium alloy made by mechanical alloying

Mechanical alloying is a unique high energy milling process for producing metal powders with a controlled microstructure. When applied to aluminum based alloys, a uniform, equiaxed fine dispersion of oxygen- and carbon-based particles is obtained. In addition, a very fine grain structure, pinned by the dispersoid, is generated. Relatively low volume loadings of dispersoid may be employed to achieve attractive combinations of properties including ambient temperature tensile strength, corrosion resistance and stress corrosion cracking resistance. The development of a dispersion strengthened aluminum-4 pct magnesium alloy is discussed.     

含Er镁合金的研究进展

综述了稀土元素Er在镁合金中的作用及对镁合金显微组织、力学性能和耐蚀性能影响的研究进展.Er可以净化镁合金熔体并对熔体具有良好的阻燃作用;稀土Er可以细化合金的晶粒组织,影响析出相的形态、数量、大小和分布,提高了镁合金的力学性能和耐腐蚀性能.     

Stress corrosion cracking of aluminum alloys

Stress corrosion cracking of aluminum alloys is reviewed. An extensive failure analysis shows how many service failures occurred in the aerospace industry over a ten year period and what kind of alloys and stresses led to initiation and propagation of stress corrosion cracks which caused these service failures. The paper contains most of the results of stress corrosion tests with aluminum alloys that have been obtained to date with fracture mechanics techniques. Stress corrosion crack growth rate measurements are compared with the results from smooth specimen testing and it is shown that the correlation between the different test results is very satisfactory. The present and limited status of theoretical understanding of stress corrosion cracking is outlined. A major part of the paper is devoted to the results of the latest alloy development. High strength aluminum alloys of dramatically increased stress corrosion resistance are available now. In the near future, stress corrosion resistant alloys of even higher strength might become available. What is still lacking is a detailed understanding of the mechanisms by which stress corrosion cracks initiate and propagate.     

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.     

Stress corrosion cracking of aluminum alloys

Stress corrosion cracking of aluminum alloys is reviewed. An extensive failure analysis shows how many service failures occurred in the aerospace industry over a ten year period and what kind of alloys and stresses led to initiation and propagation of stress corrosion cracks which caused these service failures. The paper contains most of the results of stress corrosion tests with aluminum alloys that have been obtained to date with fracture mechanics techniques. Stress corrosion crack growth rate measurements are compared with the results from smooth specimen testing and it is shown that the correlation between the different test results is very satisfactory. The present and limited status of theoretical understanding of stress corrosion cracking is outlined. A major part of the paper is devoted to the results of the latest alloy development. High strength aluminum alloys of dramatically increased stress corrosion resistance are available now. In the near future, stress corrosion resistant alloys of even higher strength might become available. What is still lacking is a detailed understanding of the mechanisms by which stress corrosion cracks initiate and propagate. Brown Boveri Research Center, Baden, Switzerland This paper is based on an invited presentation made at a symposium on “Advances in the Physical Metallurgy of Aluminum Alloys” held at the Spring Meeting of TMS-IMD in Philadelphia, Pennsylvania, on May 29 to June 1, 1973. The symposium was co-sponsored by the Physical Metallurgy Committee and the Non-Ferrous Metals Committee of TMS-IMD.     

Influence of Nd and Y additions on the corrosion behaviour of extruded Mg-Zn-Zr alloys

To improve the corrosion resistance of wrought magnesium alloys through rare earth (RE) additions, the corrosion behaviour of Mg-5Zn-0.3Zr-xNd (x=0, 1, and 2; wt%) and Mg-5Zn-0.3Zr-2Nd-yY (y=0.5 and 1; wt%) alloys in a 5wt% NaCl solution was investigated using immersion test and electrochemical measurements. The results of immersion test show that Mg-5Zn-0.3Zr-2Nd alloy exhibits the best corrosion resistance among the tested alloys. Electrochemical measurements show that secondary phases in RE-containing Mg-5Zn-0.3Zr alloys behave as less noble cathodes in micro-galvanic corrosion and suppress the cathodic process. The additions of Nd and Y into Mg-5Zn-0.3Zr alloy also improve the compactness of the corrosion product film and are beneficial to the corrosion resistance.     

Developing an Empirical Relationship to Predict Corrosion Rate of AZ31B Magnesium Alloy under Sodium Chloride Environment

Magnesium alloys have gained considerable interest as a structural material for automotive and aerospace applications due to their low-density, high specific strength and good castability. As a consequence, these light alloys have a promising future. The limitation of low corrosion resistance restricts their practical applications. Corrosion behaviour of the AZ31B magnesium alloy was evaluated by conducting immersion corrosion test in NaCl solution at different chloride ion concentrations, pH value and immersion time. An attempt was also made to develop an empirical relationship to predict the corrosion rate of AZ31B magnesium alloy. Three factors, five level, central composite rotatable design matrix was used to minimize the number of experimental conditions. Response surface methodology was used to develop the relationship. The developed relationship can be effectively used to predict the corrosion rate of AZ31B magnesium alloy at 95 % confidence level.     

Investigation of stress corrosion crack growth in Mg alloys using J-integral estimations

Crack growth resistance curves have been determined for the stress corrosion cracking of two magnesium alloys in which theJ-integral is plotted against crack extension. As determined in this way, the resistance to crack growth initially falls with decreasing applied displacement rate but rises again at the slower rates. The effect is in line with previous results obtained on plain specimens and is thought to be due to increasing passivation at the slower testing rates. The results are discussed in terms of the displacement and displacement rate occurring at the tip of the moving crack. Formerly with The University of Newcastle upon Tyne     

Progress in Research on Vanadate-Based Coatings on Corrosion Resistance

Vanadate, usually used as the corrosion resistant inhibitor for the paint systems, is one of the substances that have been proposed as alternative to toxic chromate for the corrosion protection. In this paper, the possibility of vanadate passivating from its chemical properties was introduced firstly. Then, the progress and examples in research on vanadate conversion coatings on the corrosion resistance were summarized. And the substrates discussed here contained aluminum alloys, magnesium alloys and so on. Finally, the research tendency of vanadate-based coatings was discussed.     

Effect of samarium on microstructure and corrosion resistance of aged as-cast AZ92 magnesium alloy

The effects of samarium（Sm） on microstructure and corrosion resistance of AZ92 magnesium alloy were characterized and analyzed by scanning electronic microscopy, X-ray diffraction, mass loss test, electrochemical impedance spectroscopy, X-ray photoelectron spectroscopy and potentio-dynamic polarization test. The results showed that the added Sm could promote continuous precipitation of β-Mg17Al12 phase in grains, and meanwhile restrain discontinuous precipitation of the same phase along the grain boundaries. Thus, the precipitations distributed more uniformly in the aged AZ92 magnesium alloys. When the content of Sm was 0.5 wt.%, the corrosion resistance of aged AZ92 alloy tended to be the best, which was due to the β-phase distributes more homogeneous reducing the galvanic corrosion. The corrosion product film had more integrality and compactness than AZ92 alloys without Sm. However, it resulted in worse corrosion resistance of AZ92 alloy because of the formation of mass cathodic Al2 Sm phase coming from excess Sm in AZ92 alloy.