包铝层对铝合金搅拌摩擦焊焊缝电化学腐蚀行为影响
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摘要
搅拌摩擦焊(Friction stir welding,FSW)是英国焊接研究所(The welding institute,TWI)在1991年提出的一种新型固相焊接技术。搅拌摩擦焊技术被广泛应用于航天工业、轨道交通与陆路交通工业、汽车工业等其他行业。目前国内外关于铝合金搅拌摩擦焊研究报道比较多,但主要集中于焊接工艺以及力学性能的研究,对铝合金搅拌摩擦焊焊缝的腐蚀性能研究报道较少,特别是包铝层对铝合金搅拌摩擦焊焊缝电化学腐蚀行为影响更鲜有报道。
本论文主要研究含有包铝层的2B06、2524、7B04和7075等航空用铝合金的搅拌摩擦焊焊缝在室温0.2mol/L NaHSO_3+0.6mol/L NaCl溶液中的腐蚀行为的影响。通过室温静态失重(质量法)、扫描电镜(SEM)表面形貌观察以及动电位极化曲线等手段研究其腐蚀性能,然后在同等实验条件下与母材进行了对比研究,并且进行了FSW接头的显微组织和显微硬度分布试验,为改善搅拌摩擦焊焊接工艺设计与腐蚀防护措施提供参考依据。
通过上述试验研究得出,微观区域显微组织形态的不同,成为影响显微硬度分布和腐蚀行为的主要因素。接头硬度分布曲线呈现“W”型,两边母材区硬度最高,并且焊缝局部区域出现了软化。静态失重试验表明,包铝层平均腐蚀速率最小,母材平均腐蚀速率最大,搅拌摩擦焊接头平均腐蚀速率较母材的小。表面形貌(SEM)分析表明,包铝层与接头出现较少的点蚀坑,母材出现较大的疏松的腐蚀坑。动电位极化曲线测试表明,包铝层腐蚀电位Ecorr最低,腐蚀电流Icorr最小,搅拌摩擦焊接头与母材相比,腐蚀电位Ecorr较负,腐蚀电流Icorr较小。
Friction stir welding(FSW) was invented at The Welding Institute (TWI) of UK in 1991 as a solid-state joining technique .The friction stir welding technology is widely applied in the space industry,the orbital transportation and the overland communication industry,the automobile industry and other professions. Meanwhile, many researchers have devoted to systematically investigating the technology and the mechanical properties of FSW joints, the electrochemical corrosion behaviors have been studied relatively scarcely.
In the scope of this thesis,influence of Al clad on electrochemical corrosion behavior of friction stir welding weld of 2B06,2524,7B04 and 7075 aluminum alloy have been researched . By static weight loss experiment (gravimetric test),potentiodynamic polarization curve and surface topography analysis(SEM),in the ambient temperature solution of 0.2M NaHSO3 and 0.6M NaCl, corrosion performance was investigated. Then, at the same given experimental conditions,friction stir welding weld and parent metal were comparatively investigated. Meanwhile,the joint of friction stir welding microhardness distribution and microstructure were studied.
Test results showed that the microstructure variation of friction stir welding was the main reason for corrosion resistance and microhardness distribution.The microhardness profile of friction stir welding appeared“W”form, microhardness of both parent material was the highest,and softer region of friction stir welding appeared in some particular zones. Static weight loss experiment (gravimetric test) indicated that the corrosion rate of parent material(Al clad) was the least. Scanning electron microscope (SEM) observation showed that a few shallow pits presented on the surface of the FSW weld and parent material(Al clad), however,a large number of deeper pits emerged on the surfaces of parent material.The potentiodynamic polarization curve showed that the corrosion potentials of the parent material(Al clad)were less positive than those of the FSW weld and parent material, meanwhile, the corrosion current density were less than those of the FSW weld and parent material. Friction stir welding weld had more negative corrosion potential and lower corrosion current compared with the base metal.
本论文主要研究含有包铝层的2B06、2524、7B04和7075等航空用铝合金的搅拌摩擦焊焊缝在室温0.2mol/L NaHSO_3+0.6mol/L NaCl溶液中的腐蚀行为的影响。通过室温静态失重(质量法)、扫描电镜(SEM)表面形貌观察以及动电位极化曲线等手段研究其腐蚀性能,然后在同等实验条件下与母材进行了对比研究,并且进行了FSW接头的显微组织和显微硬度分布试验,为改善搅拌摩擦焊焊接工艺设计与腐蚀防护措施提供参考依据。
通过上述试验研究得出,微观区域显微组织形态的不同,成为影响显微硬度分布和腐蚀行为的主要因素。接头硬度分布曲线呈现“W”型,两边母材区硬度最高,并且焊缝局部区域出现了软化。静态失重试验表明,包铝层平均腐蚀速率最小,母材平均腐蚀速率最大,搅拌摩擦焊接头平均腐蚀速率较母材的小。表面形貌(SEM)分析表明,包铝层与接头出现较少的点蚀坑,母材出现较大的疏松的腐蚀坑。动电位极化曲线测试表明,包铝层腐蚀电位Ecorr最低,腐蚀电流Icorr最小,搅拌摩擦焊接头与母材相比,腐蚀电位Ecorr较负,腐蚀电流Icorr较小。
Friction stir welding(FSW) was invented at The Welding Institute (TWI) of UK in 1991 as a solid-state joining technique .The friction stir welding technology is widely applied in the space industry,the orbital transportation and the overland communication industry,the automobile industry and other professions. Meanwhile, many researchers have devoted to systematically investigating the technology and the mechanical properties of FSW joints, the electrochemical corrosion behaviors have been studied relatively scarcely.
In the scope of this thesis,influence of Al clad on electrochemical corrosion behavior of friction stir welding weld of 2B06,2524,7B04 and 7075 aluminum alloy have been researched . By static weight loss experiment (gravimetric test),potentiodynamic polarization curve and surface topography analysis(SEM),in the ambient temperature solution of 0.2M NaHSO3 and 0.6M NaCl, corrosion performance was investigated. Then, at the same given experimental conditions,friction stir welding weld and parent metal were comparatively investigated. Meanwhile,the joint of friction stir welding microhardness distribution and microstructure were studied.
Test results showed that the microstructure variation of friction stir welding was the main reason for corrosion resistance and microhardness distribution.The microhardness profile of friction stir welding appeared“W”form, microhardness of both parent material was the highest,and softer region of friction stir welding appeared in some particular zones. Static weight loss experiment (gravimetric test) indicated that the corrosion rate of parent material(Al clad) was the least. Scanning electron microscope (SEM) observation showed that a few shallow pits presented on the surface of the FSW weld and parent material(Al clad), however,a large number of deeper pits emerged on the surfaces of parent material.The potentiodynamic polarization curve showed that the corrosion potentials of the parent material(Al clad)were less positive than those of the FSW weld and parent material, meanwhile, the corrosion current density were less than those of the FSW weld and parent material. Friction stir welding weld had more negative corrosion potential and lower corrosion current compared with the base metal.
引文
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[6]傅志红,贺地求,周鹏展.7A52铝合金搅拌摩擦焊焊缝的组织分析[J] .焊接学报,2006,5,65-68
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[8]王希靖,叶结和.不锈钢搅拌摩擦焊的研究现状与发展趋势[J].现代焊接,2007, 50(2):1-3
[9]胡学安,徐道荣.镁合金搅拌摩擦焊研究现状及进展[J].轻合金加工技术,2006, 10, 11-15
[10]刘小文,陈丹,鄢君辉.LF6-LY12搅拌摩擦焊接头组织性能分析[J].机械科学与技术,2003, 23(12):1430-1432
[11]沈洋,王快社,吕爽.7075铝合金搅拌摩擦焊研究[J] .特种铸造及有色合金,2007,27(2),145-148
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[13]贺永海,张立武.搅拌摩擦焊用搅拌头的研究进展[J].航天制造技术,2005,10(5),47-51
[14]李兵,谢里阳,张君一.2A12铝合金搅拌摩擦焊工艺与焊缝组织特性分析[J].工艺与检测,2008,1,69-73
[15]周鹏展,贺地求,舒霞云.搅拌摩擦焊工艺参数对2519厚板焊接性能的影响[J].工艺技术,2005,4,33-35
[16]柯黎明,邢丽,刘鸽平.搅拌摩擦焊工艺及其应用[J].南昌航空工业学院学报,1999,13(3): 1-5
[17]张胜玉.搅拌摩擦焊原理及应用[J].电焊机,2000,30(1):6-9
[18]柯黎明.搅拌摩擦焊工艺及应用[J].工艺与新技术,2000,29(2):7-8
[19] Benedyk JC.TMS 2001:Aluminum joining technology for transportation and structural applications .Light Metal Age, 2001,59:48
[20] Mendez.P.F,Eagar.T.W. Welding processes for aeronautics [J].Adv Mater Proc.2001,159(5):39
[21]赵衍华,林三宝,吴林.搅拌摩擦焊应用及焊接设备简介[J].电焊机,2004,1,7-11
[22]王训宏,王快社.搅拌摩擦焊的发展现状及存在的问题[J].焊接技术,2006,12,1-4
[23] Davenport John.搅拌摩擦焊技术已在欧洲推广应用[J].国外机车车辆工艺,2002,(4):14
[24]易奇.浅谈搅拌摩擦焊技术及应用[J].化工职业技术教育,2007,1,30-33
[25]张敏,黄红军,李志广.金属腐蚀监测技术[J].腐蚀科学与防护技术,2007,9,354-356
[26] Jariyaboon M ,Davenport A J, Ambat R, et al.The effect of welding parameters on the corrosion behavior of friction stir welded AA2024-T351[J].Corros Sci.2007,47:877
[27]黄华,董仕节,吴勇.LF21板搅拌摩擦焊接头组织与焊接工艺关系的研究[J].热加工工艺,2006,35(3),1-3
[28] P. Bala Srinivasan, W. Dietzel. Stress corrosion cracking susceptibility of friction stir weldedAA7075–AA6056 dissimilar joint [J]. Materials Science and Engineering, A 392 (2005):292–300
[29] Barbara N, Padgett Christian Paglia. Characterization of Corrosion Behavior in Friction Stir Weld Al-Li-CuAF/C458 Alloy[J]. The Minerals, Metals & Materials Society,2004 (35):301-302
[30] P.S.Pao,S.J.Gill,C.R.Feng. Corrosion-fatigue crack growth in friction stir welded Al7050[J].Scripta Materialia 2001(45):601-612
[31] D.A.Wadeson, X. Zhou. Corrosion behavior of friction stir welded AA7108 T79 aluminum alloy[J].Corrosion Science 48 (2006) 887–897
[32]赵亚东,沈长斌,刘书华,等.6082铝合金搅拌摩擦焊焊缝的电化学腐蚀行为[J].焊接学报,2008(29),10,105-107
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