钬改性AZ91镁合金组织和性能的研究
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摘要
本研究采用合金化方法,在AZ91镁合金中加入稀土Ho来改善其抗腐蚀性能。通过扫描电子显微镜观察、X射线衍射物相分析、拉伸实验、硬度实验、腐蚀失重试验和溶液电偶试验,研究了Ho对镁合金微观组织、机械性能和耐蚀性能的影响,NaCl溶液浓度以及耦接材料对镁合金耐蚀性的影响。结果表明,加入稀土Ho后镁合金有新相Al2Ho生成,合金组织得到细化,β相由不完全离异共晶变为完全离异共晶,二次析出β相的形成得到抑制;镁合金抗拉强度、屈服强度、宏观硬度和α相硬度得到提高,断裂机制从解理断裂转变为准解理断裂;抗浸泡腐蚀性能和抗电偶腐蚀性能得到提高,并且氯离子浓度越大,镁合金的耐蚀性越差,镁合金与QT400-15球墨铸铁和45号钢耦接时腐蚀严重,因此,实际应用中应尽量避免镁合金件与其直接接触。综合机械性能、抗腐蚀性能和经济性,在实验Ho含量范围内AZ91Ho3镁合金的性能最佳。
Magnesium alloys are widely used in aviation, automobile, electron and other fields due to their light density, good dimensional stability, excellent mechanical property and shielding electromagnetic interference property. Application in engineering is limited due to its inherent drawbacks, however, such as low elastic modulus, poor plasticity and corrosion resistant properties and so on. Poor corrosion resistant property is the most important factor that restricts to its application. Therefore, it is important to study the anticorrosion properties and push the development of magnesium alloys applications.
Nowadays, most of the anticorrosion researches are focused on the surface protection magnesium alloy and so in the state of passivity. Surface anticorrosion technology is just for some specifically condition or accessory. Such one-to-one corrosion control method can not meet apparently the enlarging of magnesium alloys application fields.
Alloying addition agent can modify the phase structure and matrix corrosion potential of Magnesium alloy and thus it is an important and essential way to improve the corrosion resistant properties of Magnesium alloys. Consequently, this paper adopted alloying method and added rare earth element Ho into Magnesium alloys in order to improve their anticorrosion properties. Five kinds of heterogeneous Magnesium alloys are AZ91、AZ91+0.1wt.%Ho、AZ91+1.0wt.%Ho、AZ91+2.0wt.%Ho and AZ91+3.0wt.% Ho respectively.
The microstructure and phase of magnesium alloys have been analyzed by scanning electronic microscope (SEM) and X-ray diffraction (XRD). The results indicated that there wereαphase,β(Mg17Al12)phase and Al2Ho phase coexisted in Magnesium alloys added with rare earth element Ho. With the addition of rare earth element Ho, the microstructure refined into grain state from bulky bones state and the size of crystal grain decreased; discontinuous reticularβphases distribute over the grain boundary ofα-Mg phase, its eutectic mode have changed into fully-divorced eutectic from partially-divorced eutectic. The formation of second separationβphases is restricted. Tensile and hardness tests showed that rare earth element Ho improved the tensile strength, yield strength and hardness of AZ91 magnesium alloys. The fracture mechanism changed from cleavage fracture to quasi-cleavage fracture. The AZ91 magnesium alloy with 2.0wt.% rare earth element Ho has the best microstructure and mechanical properties in this test.
Magnesium alloys are widely used in aviation, automobile, electron and other fields due to their light density, good dimensional stability, excellent mechanical property and shielding electromagnetic interference property. Application in engineering is limited due to its inherent drawbacks, however, such as low elastic modulus, poor plasticity and corrosion resistant properties and so on. Poor corrosion resistant property is the most important factor that restricts to its application. Therefore, it is important to study the anticorrosion properties and push the development of magnesium alloys applications.
Nowadays, most of the anticorrosion researches are focused on the surface protection magnesium alloy and so in the state of passivity. Surface anticorrosion technology is just for some specifically condition or accessory. Such one-to-one corrosion control method can not meet apparently the enlarging of magnesium alloys application fields.
Alloying addition agent can modify the phase structure and matrix corrosion potential of Magnesium alloy and thus it is an important and essential way to improve the corrosion resistant properties of Magnesium alloys. Consequently, this paper adopted alloying method and added rare earth element Ho into Magnesium alloys in order to improve their anticorrosion properties. Five kinds of heterogeneous Magnesium alloys are AZ91、AZ91+0.1wt.%Ho、AZ91+1.0wt.%Ho、AZ91+2.0wt.%Ho and AZ91+3.0wt.% Ho respectively.
The microstructure and phase of magnesium alloys have been analyzed by scanning electronic microscope (SEM) and X-ray diffraction (XRD). The results indicated that there wereαphase,β(Mg17Al12)phase and Al2Ho phase coexisted in Magnesium alloys added with rare earth element Ho. With the addition of rare earth element Ho, the microstructure refined into grain state from bulky bones state and the size of crystal grain decreased; discontinuous reticularβphases distribute over the grain boundary ofα-Mg phase, its eutectic mode have changed into fully-divorced eutectic from partially-divorced eutectic. The formation of second separationβphases is restricted. Tensile and hardness tests showed that rare earth element Ho improved the tensile strength, yield strength and hardness of AZ91 magnesium alloys. The fracture mechanism changed from cleavage fracture to quasi-cleavage fracture. The AZ91 magnesium alloy with 2.0wt.% rare earth element Ho has the best microstructure and mechanical properties in this test.
引文
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[3].朱祖芳等.有色金属的耐腐蚀性及其应用.北京,化学工业出版社,1995.6
[4].陶令恒等.铸造手册(非铁合金卷).机械工业出版社,1994,166.
[5]张永君,严川伟,王福会等,镁的应用及其腐蚀与防护,材料保护,2002,35(4):4~6
[6] 轻合金加工材料编写组.轻金属材料加工手册.北京:冶金工业出版社,1980: 162~180
[7]曾小勤,王渠东,吕宜振等,镁合金应用新进展,铸造,1998,11:39~43
[8]黄光胜,范永革,汤爱涛等,镁及镁合金腐蚀最新研究进展,材料导报,2002,16(4):38~40
[9] Rappaz M, Modelling of microstructure formation in solidification process, Int Mater Rev, 1989, 34(3):113~117
[10]张永君,镁及镁合金环保型阳极氧化表面改性技术研究.中国科学院金属研究所博士学位论文,2003,2
[11]李新林,王慧远,姜启川.颗粒增强镁基复合材料的研究现状及发展趋势.材料科学与工艺,2001,9(2):219~224
[12]刘正,王越,王中光等.镁基轻质材料的研究与应用.材料研究学报,2000,14(5):449~456
[13]吴镇宁,李培杰,刘树勋等.镁合金腐蚀问题研究现状.铸造,2001,50(10):583~586
[14]许越,赵连城.镁合金表面的腐蚀特性及其防护技术.哈尔滨工业学学报,2001,33(6):753~755:
[15] S. Mathieu, C. Rapin, A corrosion study of the main constituent phases of AZ91 magnesium alloys, Corrosion Science. 2003, 45, 2741~2755
[16] O.Lunder, J.E.Lein, T.Kr.Aune, K.Nisancioglu, Corrosion. 1989, 45, 741~743
[17] Robert.S.Bush, Magnesium Products Design. Sponsored by the International Magnesium Association New York, M.Dekker. 1987, 497~529.
[18] 战广深,肖向辉,Mg-Al-Zn-Mn 合金在 NaCl 溶液中的接触腐蚀行为,上海有色金属.1996,17(1):8~11
[19] 蔡启舟,王立世,NaCl 水溶液中 AZ91 与 A3 钢的接触腐蚀,特种铸造及有色合金,2004,1:31~33
[20] Guangling Song, Birgir Johannesson, Galvanic corrosion of magnesium alloy AZ91D in contact with an aluminium alloy, steel and zinc, Corrosion Science. 2004, 46: 955~977.
[21] M. Starostin, A. Smorodin, Y. Cohen, L. Gal-Or, S. Tamir, Galvanic corrosion of magnesium alloys,in: E. Aghion, D. Eliezer (Eds.), Magnesium 2000, Proceedings of the Second Israeli International Conference on Magnesium Science and Technology, Dead Sea, Israel, 2000, 363~370.
[22] G. Gao, G. Cole, M. Richetts, J. Balzer, P. Frantzeskakis, Effects of fastener surface on galvanic corrosion of automotive magnesium components, in: E. Aghion, D. Eliezer (Eds.), Magnesium 2000,Proceedings of the Second Israeli International Conference on Magnesium Science and Technology,Dead Sea, Israel, 2000, 321~338.
[23] J. Senf, E. Broszeit, M. Gugau, C. Berger, Corrosion and galvanic corrosion of die casted magnesium alloys, in: H.I. Kaplan, J. Hryn, B. Clow (Eds.), Magnesium Technology 2000, TMS, Nashville, 2000, 137~142.
[24]林高,彭大暑.AZ91D 镁合金耐腐蚀性能研究.矿冶工程, 2001,21(3): 79~81.
[25] Guangling Song, Andrej Atrens, Influence of microstructure on the corrosion of die-cast AZ91D, Corrosion Science. 1999, 41: 249~273.
[26]罗兵辉,谢绍俊.铸造铝镁合金的应力腐蚀.中南工业大学学报,1998, 29(6):570~572.
[27] 朱日彰等,金属腐蚀学,冶金工业出版社,1989, 306~307.
[28] BARIL G, PEBERE N. The corrosion of pure Magnesium in aerated and sodium sulphate solution [J]. Corrosion Science, 2001, 43: 471~484
[29]G. L. Makar,J.Kruger. Corrosion of Magnesium, International Materials Reviews, 1993, 38(3):138~153
[30] L. Brown.UK company leads the way in magnesium plating. Finishing, 1994, (11): 22~23
[31]韩克平,方景礼.氟离子对化学镀镍的加速机理.电镀与环保,1996,16(3):21~24。
[32]焦树强,旷亚非等.镁及其合金的腐蚀与阳极化处理.电镀与环保,2002,22(3):1~4
[33]曹楚南.腐蚀电化学原理.北京:化学工业出版社,1989,152
[34]李瑛,宋光铃,林海潮等.金属镁在腐蚀介质中界面结构特征与负差数效应关系研究.腐蚀科学与防护技术,1999,11(4):4~10
[35] SongG .L ,Atrens A ,Stjohn Detal .The Electrochemical Corrosion of Pure Magnesium in 1N NaCl.Corros.Sci.,1997, 39: 835~853
[36]王之清.国外镁合金压铸技术的发展.铸造,1997,(8): 48~51
[37]王祝堂.德国的镁研究计划.轻金属加工技术,1997,(25):44~48
[38]张君尧,韩秉诚.镁合金的应用.国外轻金属,1980,(6):38~45
[39] R.A mbat,N .A ung,W .Zhou. Evaluation of Microstructural Effects on Corrosion behaviour of AZ91D Magnesium Alloy. Corros.Sci., 2000, 42:1433~1455
[40] D. Daloz, P. Steinmetz, G. Michot, Corrosion. 1997, 53, 944.
[41] J. Campbell, Castings, Butterworth Heinemann. 1991.
[42] Boyer, H.E. and Gall, T.L. Metals Handbook. Mwtals Park, Ohio, 1985.
[43] R. Lindstrom, J.E. Svensson, L.G. Johansson, J. Electrochem. Soc. 2002, 149, B103.
[44]肖纪美,应力作用下的金属腐蚀,化学工业出版社,1990,188.
[45] R. Tunold, H. Holtan and M.B. Hagg Berge, Corros. Sci. 1997, 17, 353.
[46] G. Song, A. Atrens, D. ST John, Z. Wu and J. Nairn, The Anodic Dissolution of Magnesium in Chloride and Sulphate Solutions, Corrosion Science, 1997, Vol.39, NO.10~11.
[47] A. Froats, T.K. Aune, W. Unsworth, Corrosion of Magnesium and Magnesium Alloys, Corrosion, Vol13,ASM Handbook, ASM International, 1987, 740~754.
[48] 罗志平,稀土在镁合金溶液中作用的热力学分析,中国稀土学报,1995,13(2):119~122.
[49] 曾荣昌,柯伟.镁合金的最新发展及应用前景.金属学报,2001,37(7):673~685
[50] 张勇,许越,周瑞德.稀土铈对AZ91镁合金表面腐蚀性能的影响.哈尔滨工业大学学报,2002,34(3):376~378
[51] Sunghak Lee, Seung Hyuk Lee, Do Hyang Kim. Effect of Y, Sr, and Nd additions on the Microstructure and Micro-fracture Mechanism of Squeeze-Cast AZ91-X Magnesium Alloys. Metallurgical and Materials Transaction, 1998, 29: 12~35.
[52] 中津川动 . マクネシウム合金の耐蚀性るよび表面处理方法 . まて.1999(4):291~293
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