<strong>2xxx</strong>系铝合金第二相对搅拌摩擦焊接头腐蚀行为的影响

doi:10.11902/1005.4537.2022.354

中国腐蚀与防护学报

2023, Vol. 43

Issue (6): 1247-1254 CSTR: 32134.14.1005.4537.2022.354 DOI: 10.11902/1005.4537.2022.354

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2xxx系铝合金第二相对搅拌摩擦焊接头腐蚀行为的影响

钟嘉欣¹, 关蕾¹(

), 李雨², 黄家勇², 石磊³

^1.广东工业大学省部共建精密电子制造技术与装备国家重点实验室广州市非传统制造技术及装备重点实验室广州 510006
^2.中船黄埔文冲船舶有限公司广东省舰船先进焊接技术企业重点实验室广州 510715
^3.山东大学材料液固结构演变与加工教育部重点实验室济南 250061

Effect of Second Phase on Corrosion Behavior of Friction-stir-welded Joints of 2xxx Series Al-alloy

ZHONG Jiaxin¹, GUAN Lei¹(

), LI Yu², HUANG Jiayong², SHI Lei³

^1.Guangzhou Key Laboratory of Nontraditional Machining and Equipment, State Key Laboratory of Precision Electronic Manufacturing Technology and Equipment, Guangdong University of Technology, Guangzhou 510006, China
^2.CSSC Huangpu Wenchong Shipbuilding Company Limited, Guangdong Provincial Key Laboratory of Advanced Welding Technology for Ships, Guangzhou 510715, China
^3.Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials (Ministry of Education), Shandong University, Jinan 250061, China

引用本文:

钟嘉欣, 关蕾, 李雨, 黄家勇, 石磊. 2xxx系铝合金第二相对搅拌摩擦焊接头腐蚀行为的影响[J]. 中国腐蚀与防护学报, 2023, 43(6): 1247-1254.
Jiaxin ZHONG, Lei GUAN, Yu LI, Jiayong HUANG, Lei SHI. Effect of Second Phase on Corrosion Behavior of Friction-stir-welded Joints of 2xxx Series Al-alloy[J]. Journal of Chinese Society for Corrosion and protection, 2023, 43(6): 1247-1254.

全文: PDF(4612 KB) HTML

摘要:

搅拌摩擦焊 (FSW) 作为一种固态连接工艺，有效解决了工程应用上2xxx系铝合金的焊接难题。然而由于搅拌摩擦焊过程中接头各个区域所经历的热力作用不同，FSW接头显微组织在各个区域发生演化，进而导致接头腐蚀行为和机理存在明显差异。本文总结了2xxx系铝合金搅拌摩擦焊接头的腐蚀类型、腐蚀发生区域及诱因，并概述了改善焊接接头耐蚀性的方法。

关键词 ：搅拌摩擦焊, 铝合金, 微观组织, 腐蚀行为

Abstract：

Friction stir welding, as a solid state bonding process, can effectively solve the welding problems of 2xxx series Al-alloy in engineering applications. However, during friction stir welding process, every local area of the welded joint has experienced distinctive thermal cycling and material plastic flow, therefore, different local areas may exhibit obviously differences in their microstructure evolution, as well as in corrosion behavior and corrosion mechanism. In this paper, the corrosion types, positions of corrosion initiation and relevant inducing factors for friction stir welded joints of 2xxx series Al-alloy were reviewed, meanwhile, the relevant corrosion mechanism of weld joints and corresponding methods of improving corrosion resistance for the welded joints were also summerized.

Key words： friction stir welding Al-alloy microstructure corrosion behavior

收稿日期: 2022-11-16 32134.14.1005.4537.2022.354

ZTFLH:

TG 174

基金资助:广东省自然科学基金(2021A1515010967);广州市科技计划项目(202102020723);广州市科技计划项目(202102020626);中国博士后科学基金(2020M682929)

通讯作者: 关蕾，E-mail: lguan@gdut.edu.cn，研究方向为金属材料的腐蚀与防护

Corresponding author: GUAN Lei, E-mail: lguan@gdut.edu.cn

作者简介: 钟嘉欣，女，1999年生，硕士生

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图1 搅拌摩擦焊过程示意图[2]

表1 两类第二相的EDS分析结果[15] (atomic fraction / %)

图2 抛光后的2024铝合金SEM图像[12]

图3 FSW过程中生成的宏观结构，后退侧的TMAZ结构和HAZ结构及前进侧的TMAZ结构[28]

表2 2xxx系铝合金搅拌摩擦焊接头腐蚀行为总结

表3 提高2xxx系铝合金搅拌摩擦焊接头耐腐蚀性的方法总结

1	Majeed T, Mehta Y, Siddiquee A N. Precipitation-dependent corrosion analysis of heat treatable aluminum alloys via friction stir welding, a review [J]. Proc. Inst. Mech. Eng., 2021, 235C: 7600
2	Threadgill P L, Leonard A J, Shercliff H R, et al. Friction stir welding of aluminium alloys [J]. Int. Mater. Rev., 2009, 54: 49 doi: 10.1179/174328009X411136
3	Mishra R S, Ma Z Y. Friction stir welding and processing [J]. Mater. Sci. Eng., 2005, 50R: 1
4	Benavides S, Li Y, Murr L E, et al. Low-temperature friction-stir welding of 2024 aluminum [J]. Scr. Mater., 1999, 41: 809 doi: 10.1016/S1359-6462(99)00226-2
5	Jonckheere C, de Meester B, Denquin A, et al. Torque, temperature and hardening precipitation evolution in dissimilar friction stir welds between 6061-T6 and 2014-T6 aluminum alloys [J]. J. Mater. Process. Technol., 2013, 213: 826 doi: 10.1016/j.jmatprotec.2013.01.001
6	Wang S C, Starink M J. Precipitates and intermetallic phases in precipitation hardening Al-Cu-Mg- (Li) based alloys [J]. Int. Mater. Rev., 2005, 50: 193 doi: 10.1179/174328005X14357
7	Fan G H, Geng L, Meng Q C, et al. The characterization and formation mechanism of nanosized insoluble intermetallic phase in 2024Al alloy [J]. Mater. Chem. Phys., 2010, 122: 200 doi: 10.1016/j.matchemphys.2010.02.034
8	Liang M C, Chen L, Zhao G Q, et al. Effects of solution treatment on the microstructure and mechanical properties of naturally aged EN AW 2024 Al alloy sheet [J]. J. Alloy. Compd., 2020, 824: 153943 doi: 10.1016/j.jallcom.2020.153943
9	Hutchinson C R, Ringer S P. Precipitation processes in Al-Cu-Mg alloys microalloyed with Si [J]. Metall. Mater. Trans., 2000, 31A: 2721
10	Li J Y, Chen S Y, Li F S, et al. Synergy effect of Si addition and pre-straining on microstructure and properties of Al-Cu-Mg alloys with a medium Cu/Mg ratio [J]. Mater. Sci. Eng., 2019, 767A: 138429
11	Li J C, Birbilis N, Buchheit R G. Electrochemical assessment of interfacial characteristics of intermetallic phases present in aluminium alloy 2024-T3 [J]. Corros. Sci., 2015, 101: 155 doi: 10.1016/j.corsci.2015.09.012
12	Kang J, Fu R D, Luan G H, et al. In-situ investigation on the pitting corrosion behavior of friction stir welded joint of AA2024-T3 aluminium alloy [J]. Corros. Sci., 2010, 52: 620 doi: 10.1016/j.corsci.2009.10.027
13	Wang X J, Ma X F, Zhang J Y, et al. Corrosion behavior of the friction stir weld of 2024 aluminum alloy in salt solution [J]. Corros. Prot., 2018, 39: 45
13	王希靖, 马晓飞, 张金银等. 盐水环境中搅拌摩擦焊接2024铝合金的腐蚀行为 [J]. 腐蚀与防护, 2018, 39: 45
14	Bousquet E, Poulon-Quintin A, Puiggali M, et al. Relationship between microstructure, microhardness and corrosion sensitivity of an AA 2024-T3 friction stir welded joint [J]. Corros. Sci., 2011, 53: 3026 doi: 10.1016/j.corsci.2011.05.049
15	Queiroz F M, Magnani M, Costa I, et al. Investigation of the corrosion behaviour of AA 2024-T3 in low concentrated chloride media [J]. Corros. Sci., 2008, 50: 2646 doi: 10.1016/j.corsci.2008.06.041
16	Buchheit R G, Grant R P, Hlava P F, et al. Local dissolution phenomena associated with S phase (Al₂CuMg) particles in aluminum alloy 2024‐T3 [J]. J. Electrochem. Soc., 1997, 144: 2621 doi: 10.1149/1.1837874
17	Zhang Y J, Liu H Y, Wang H B. Performance study on intergranular corrosion and exfoliation corrosion of friction stir welded joints of aluminium alloy [J]. Eng. Test, 2018, 58(3): 35
17	张亚娟, 刘海燕, 王红斌. 铝合金搅拌摩擦焊接头晶间腐蚀和剥落腐蚀性能研究 [J]. 工程与试验, 2018, 58(3): 35
18	Mu C. Intergranular corrosion of Al-Cu-Mg high-strength aluminum alloy [J]. Alum. Fabr., 2017, (6): 22
18	牟春. Al-Cu-Mg系高强铝合金的晶间腐蚀 [J]. 铝加工, 2017, (6): 22
19	Grilli R, Baker M A, Castle J E, et al. Localized corrosion of a 2219 aluminium alloy exposed to a 3.5% NaCl solution [J]. Corros. Sci., 2010, 52: 2855 doi: 10.1016/j.corsci.2010.04.035
20	Blanc C, Lavelle B, Mankowski G. The role of precipitates enriched with copper on the susceptibility to pitting corrosion of the 2024 aluminium alloy [J]. Corros. Sci., 1997, 39: 495 doi: 10.1016/S0010-938X(97)86099-4
21	Li J F, Zheng Z Q, Ren W D. Function mechanism of secondary phase on localized corrosion of Al alloy [J]. Master. Rev., 2005, 19 (2): 81
21	李劲风, 郑子樵, 任文达. 第二相在铝合金局部腐蚀中的作用机制 [J]. 材料导报, 2005, 19(2): 81
22	Zhu D Q, van Ooij W J. Corrosion protection of AA 2024-T3 by bis-[3-(triethoxysilyl) propyl]tetrasulfide in neutral sodium chloride solution. Part 1: corrosion of AA 2024-T3 [J]. Corros. Sci., 2003, 45: 2163 doi: 10.1016/S0010-938X(03)00060-X
23	Kang J, Dong C L, Luan G H, et al. Corrosion mechanism on top surface of friction stir welded joint of 2024 aluminum alloy [J]. J. Chin. Soc. Corros. Prot., 2011, 31: 282
23	康举, 董春林, 栾国红等. 2024铝合金搅拌摩擦焊焊缝表面腐蚀机理探索 [J]. 中国腐蚀与防护学报, 2011, 31: 282
24	Wang X J, Ma X F, Zhang L L. Effect of tool pin profile on microstructure and mechanical properties of 2024 aluminum alloy joint by friction stir welding [J]. Trans. China Weld. Inst., 2017, 38 (12): 99
24	王希靖, 马晓飞, 张亮亮. 搅拌头形状对2024铝合金接头组织及性能的影响 [J]. 焊接学报, 2017, 38(12): 99
25	Hu Z L, Wang X S, Yuan S J. Quantitative investigation of the tensile plastic deformation characteristic and microstructure for friction stir welded 2024 aluminum alloy [J]. Mater. Charact., 2012, 73: 114 doi: 10.1016/j.matchar.2012.08.007
26	Kang J, Fu R D, Luan G H. Quantitative investigation on aging phase behavior for 2024-T351 aluminum alloy during friction stir welding process [J]. Phys. Test. Chem. Anal., 2011, 47A: 199
26	康举, 付瑞东, 栾国红. 定量研究2024-T351铝合金搅拌摩擦焊过程中的时效相行为 [J]. 理化检验-物理分册, 2011, 47: 199
27	Li N, Xu Y X, Li W Y, et al. Corrosion susceptibility and mechanical properties of friction-stir-welded AA2024-T3 joints [J]. Weld. World, 2022, 66: 951 doi: 10.1007/s40194-022-01282-9
28	do Vale N L, Torres E A, de Abreu Santos T F, et al. Effect of the energy input on the microstructure and mechanical behavior of AA2024-T351 joint produced by friction stir welding [J]. J. Braz. Soc. Mech. Sci. Eng., 2018, 40: 467 doi: 10.1007/s40430-018-1372-5
29	Bocchi S, Cabrini M, D’Urso G, et al. The influence of process parameters on mechanical properties and corrosion behavior of friction stir welded aluminum joints [J]. J. Manuf. Processes, 2018, 35: 1 doi: 10.1016/j.jmapro.2018.07.012
30	Entringer J, Meisnar M, Reimann M, et al. The effect of grain boundary precipitates on stress corrosion cracking in a bobbin tool friction stir welded Al-Cu-Li alloy [J]. Mater. Lett., 2019, 2: 100014
31	Jariyaboon M, Davenport A J, Ambat R, et al. The effect of welding parameters on the corrosion behaviour of friction stir welded AA2024-T351 [J]. Corros. Sci., 2007, 49: 877 doi: 10.1016/j.corsci.2006.05.038
32	Jariyaboon M, Davenport A J, Ambat R, et al. The effect of cryogenic CO₂ cooling on corrosion behaviour of friction stir welded AA2024-T351 [J]. Corros. Eng., Sci. Technol., 2009, 44: 425
33	Sato Y S, Kokawa H, Kurihara S. Systematic examination of precipitation phenomena associated with hardness and corrosion properties in friction stir welded aluminium alloy 2024 [J]. Weld. World, 2011, 55: 39
34	Proton V, Alexis J, Andrieu E, et al. Influence of post-welding heat treatment on the corrosion behavior of a 2050-T3 aluminum-copper-lithium alloy friction stir welding joint [J]. J. Electrochem. Soc., 2011, 158: C139 doi: 10.1149/1.3562206
35	da Silva R M P, Izquierdo J, Milagre M X, et al. On the local corrosion behavior of coupled welded zones of the 2098-T351 Al-Cu-Li alloy produced by Friction Stir Welding (FSW): An amperometric and potentiometric microelectrochemical investigation [J]. Electrochimica Acta., 2021, 373: 137910 doi: 10.1016/j.electacta.2021.137910
36	Sinhmar S, Dwivedi D K. Investigation of mechanical and corrosion behavior of friction stir weld joint of aluminium alloy [J]. Mater. Today: Proc., 2019, 18: 4542
37	Donatus U, de Viveiros B V G, de Alencar M C, et al. Correlation between corrosion resistance, anodic hydrogen evolution and microhardness in friction stir weldment of AA2198 alloy [J]. Mater. Charact., 2018, 144: 99 doi: 10.1016/j.matchar.2018.07.004
38	Surekha K, Murty B S, Rao K P. Effect of processing parameters on the corrosion behaviour of friction stir processed AA 2219 aluminum alloy [J]. Solid State Sci., 2009, 11: 907 doi: 10.1016/j.solidstatesciences.2008.11.007
39	Xu W F, Ma J, Wang M, et al. Effect of cooling conditions on corrosion resistance of friction stir welded 2219-T62 aluminum alloy thick plate joint [J]. Trans. Nonferrous Met. Soc. China, 2020, 30: 1491 doi: 10.1016/S1003-6326(20)65313-4
40	Ralston K D, Birbilis N, Davies C H J. Revealing the relationship between grain size and corrosion rate of metals [J]. Scr. Mater., 2010, 63: 1201 doi: 10.1016/j.scriptamat.2010.08.035
41	Wang W, Li T Q, Wang K S, et al. Effect of travel speed on the stress corrosion behavior of friction stir welded 2024-T4 aluminum alloy [J]. J. Mater. Eng. Perform., 2016, 25: 1820 doi: 10.1007/s11665-016-1979-6
42	Naik D B, Rao C H V, Rao K S, et al. Optimization of friction stir welding parameters to improve corrosion resistance and hardness of AA2219 aluminum alloy welds [J]. Mater. Today: Proc., 2019, 15: 76
43	Sinhmar S, Dwivedi D K. Enhancement of mechanical properties and corrosion resistance of friction stir welded joint of AA2014 using water cooling [J]. Mater. Sci. Eng., 2017, 684A: 413
44	Kannusamy A S, Ramasamy R. Effect of post weld heat treatment and welding parameters on mechanical and corrosion characteristics of friction stir welded aluminium alloy AA2014-T6 [J]. Trans. Can. Soc. Mech. Eng., 2019, 43: 230 doi: 10.1139/tcsme-2018-0185
45	Zhao C Y, Zhang H, Shao T G, et al. Microstructure and corrosion behaviour of Al coating deposited by cold spraying onto FSW AA2219-T87 joint [J]. Corros. Eng., Sci. Technol., 2019, 54: 86
46	Li W Y, Jiang R R, Huang C J, et al. Effect of cold sprayed Al coating on mechanical property and corrosion behavior of friction stir welded AA2024-T351 joint [J]. Mater. Des., 2015, 65: 757 doi: 10.1016/j.matdes.2014.10.007
47	Iordachescu M, Valiente A, Caballero L, et al. Laser Shock Processing influence on local properties and overall tensile behavior of friction stir welded joints [J]. Surf. Coat. Technol., 2012, 206: 2422 doi: 10.1016/j.surfcoat.2011.10.044
48	Deng Y F, Zhang T M, Gan X W, et al. Effects of ultrasonic impact on microstructure and properties of friction stir welded aluminum alloy [J]. J. Netshape Form. Eng., 2019, 11 (5) : 78
48	邓云发, 张体明, 干贤威等. 超声冲击对铝合金搅拌摩擦焊接头组织及性能的影响 [J]. 精密成形工程, 2019, 11 (5) : 78
49	Qian S H, Zhang T M, Chen Y H, et al. Effect of ultrasonic impact treatment on microstructure and corrosion behavior of friction stir welding joints of 2219 aluminum alloy [J]. J. Mater. Res. Technol., 2022, 18: 1631 doi: 10.1016/j.jmrt.2022.03.068
50	Ma S C, Zhao Y, Zou J S, et al. The effect of laser surface melting on microstructure and corrosion behavior of friction stir welded aluminum alloy 2219 [J]. Opt. Laser Technol., 2017, 96: 299 doi: 10.1016/j.optlastec.2017.05.028
51	Zhang H, Zhao C Y, Guo Q L, et al. Microstructure and corrosion behavior of friction stir welded al alloy coated by in situ shot-peening-assisted cold spray [J]. Acta Metall. Sin. (Engl. Lett.), 2020, 33: 172 doi: 10.1007/s40195-019-00966-4
52	Wang W, Li T, Wang K, et al. Effect of travel speed on the stress corrosion behavior of friction stir welded 2024-T4 aluminum alloy [J]. J. Mater. Eng. Perform., 2016, 25(5): 1820 doi: 10.1007/s11665-016-1979-6
53	Sutton M A, Reynolds A P, Yang B C, et al. Mode I fracture and microstructure for 2024-T3 friction stir welds [J]. Mater. Sci. Eng., 2003, 354A: 6
54	Kumar P V, Reddy G M, Rao K S. Microstructure and pitting corrosion of armor grade AA7075 aluminum alloy friction stir weld nugget zone-Effect of post weld heat treatment and addition of boron carbide [J]. Def. Technol., 2015, 11: 166
55	Liu W H, Liu W B, Bao A L. Improvement of corrosion resistance of friction stir welded joint of 7N01-T5 aluminum alloy by micro-arc oxidation [J]. Trans. China Weld. Inst., 2013, 34(1): 29
55	刘万辉, 刘文彬, 鲍爱莲. 微弧氧化处理改善7N01-T5铝合金搅拌摩擦焊接头的耐蚀性能 [J]. 焊接学报, 2013, 34(1): 29
56	Ou Y C, Chen M A. Corrosion resistance of the weld joint by friction stir welding on 6061 aluminum alloy after micro-arc oxidation [J]. Electropl. Finish., 2015, 34: 719
56	欧艳春, 陈明安. 6061铝合金搅拌摩擦焊焊缝微弧氧化涂层的耐蚀性 [J]. 电镀与涂饰, 2015, 34: 719
57	Rao K P, Ram G D J, Stucker B E. Improvement in corrosion resistance of friction stir welded aluminum alloys with micro arc oxidation coatings [J]. Scr. Mater., 2008, 58: 998 doi: 10.1016/j.scriptamat.2008.01.033

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