Ô Åmass% Si 0.21 Fe 0.18 Cu 4.42 Mn 0.61 Mg 1.56 Zn 0.13 Al Ü Ø. TMAZ Leonard [11] Å 2014A- FSW2-4CX-006C FSW Õ Þ. mm/min EXCO (NaCl 234 g/l KNO 3 50

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1 31 4 Ó ¹ß «Vol.31 No «Journal of Chinese Society for Corrosion and Protection Aug Ð ßß Ù 1 1 Æ 1 Ç 1 À (1. ³ Ú Æ Å ³ Î Ü Á ± µ Þ ¼ ¼ Ý Đ ) º : 04 ¾ĐË FSW ² ± ÀÔ Ç Í½ ÅĐÙ É ² Æ ÁÖ ÅÑ FSW Đ Í SAZ Ä Ö S ± Đ ¾ É Æ ÛÆ Ü FSW Ó SAZ S ± Ë Ú ± ± Ú S ±¾Ü SAZ Mg Ç Æ ÔĐ Û Ñ : Å 04 ¾ĐË µ± Ë ¾ ÕÅ : TG17 : A» : «011Æ Åؽ ÊÖØÅ ¹Ø ¹Á ß Ø»«ÑÓ Ù ßÙ Óµ µ»ø ½ Ê Û Ê Ø ±Ô ÖÀÒ Çß ¾Ã Ê Ó Ô ÖÀ¼ ( GTAW/GMAW) ÔÏ ÖÀ ÖÀÀÕ ßØ [1] Ò 04 ½ ÊÖÀÀ Õ ² ¹ ÔÏ»ÑÓ ÄÖÀ (FSW) À¼ [] ØÐÔÍ ÇØ ÖÀ Ï [3] È Ø Åؽ Ê FSW Å Ô ÛÖ ÀÕ ÂÜÑ É»¼ ± ºÁ [4 8] FSW ÀÕ Å ÞÜ ¼ Jariyaboon [9] Å 04-T351 FSW ÀÕ HAZ ßÖÞ ³ Biallas [10] ¼ 04FSW ÀÕ TMAZ Leonard [11] Å 014A- T651 FSW ÀÕ µ TMAZ Î Æ ³ HAZ Í Åؽ Ê BM Ü Å [1,13] Ê FSW ÀÕ Å Ü ÏÄ Þ Åؽ Ê FSW Ö ÒÚ : ² : Û Ì É 009ZE5007 É ¼ : ßÓ Î 1983 ² Ã Ç ½ ÇÙ Ì FSW ³ º ¼ : ßÓ kangjusin@163.com Å ÄÐ ÙÛ Ö Ã ±Ö» Ö ¾ÓÒ Ñ Æ Ã ÒÞ Û FSW Ö Ú [14] Ó Ö Óµ Î Æ Ï Ì¼ о Ö ÀÕ Å ¼ Ï FSW ÀÕ Ï Å Ò 04 Åؽ Ê Å Ó Æ¼ [15] Ö Ì¼ Ä Ø (TEM) È (DSC) ± Æ Ö ÔÓ»Ï 1.6 mm 04 Åؽ Ê Ô Åmass% Si 0.1 Fe 0.18 Cu 4.4 Mn 0.61 Mg 1.56 Zn 0.13 Al Ü Ø 50 µm ½Å Ô Å T3 Ï ½ Í µ» «Å FSW Ó ² Ä Ø Å FSW-4CX-006C FSW Õ Þ Ö 8.05 mm Æ Æ Å Í ¹ 1.87 mm Í 1.43 mm ÖÀÁ ÕÞ 1.5 ÄÈ 700 r/min È 00 mm/min EXCO (NaCl 34 g/l KNO 3 50 g/l HNO ml/l) ϻϻÏ

2 4 Ó Þ Ò : 04 ¾ĐË Å 83 ¼ Á ASTM G34-01 ¾Ç [16] Ó EXCO Æ ± µ»ï Ò [17] Æ»ÏÒ Ó ¾» (Ç )BM Ò³ (HAZ) Ïà ½Ò³ (TMAZ-A) Üà ½Ò³ (TMAZ-R) ± Ó (SAZ) SEM»¼¾»Â EXCO 0.5 h Ä Ó SEM Ó Ó Ï» ¼ É 0.5 h ß 1 h Þ Ó Æ Ó Axiovert-00MAT Ê Æ BM HAZ ½Ò³ (TMAZ) ± SAZ Ó D/max-500/PC X Ë (XRD) BM ßÖ Å Õ Ê Ï ÓË Ê (SEM, HI- TACHI S-4800) Ï ± Ó JEOL-010 TEM Ø Ö Ë Ä Ó Ç Ê Ð Ô Ê Ð¹ 3: V» ma Ó NETSCH STA449C Î BM HAZ ± SAZ Å Ï È (DSC) ¹ 3 mm 10 mg ³ È 0 K/min Ó CHI660A Ï Ã Ý ½ BM BM ± SAZ Ûº 8 mm 10 mm È 5 mv/s Ç EXCO»Ï (4±)»Ï Ý Æ»Ï Ó 3 ݹ Æ 3.1 ÞÖ Ü ½ ÂÅà 04 ½ ÊÖ Ê Ú 1 Ö Ê ¹ÛÖÀ¼µ BM HAZ TMAZ ± SAZ 4 Ê Ú 1b e ÝÒÌ Ö Ã Ê Ó SAZ(Ú 1a ) Õ Á µ «Æ Å ± Â Ã Å Ý Å ÊÉ» Å Ø Ê Å Ú Óµ SAZ ± TMAZ È ß ¹ Ú 1b ÝÚ 1c Ò³ Ö ÛÛ 04 ½ Ê BM Ö Ê Ø Ø Ê Û ß Õ Ä Ó TMAZ (Ú 1d) ÍÛ Ã ¼ Î Õ ÓºĐÏ HAZ Û Ïà TMAZ ¹ TMAZ-D Â Ö Ã Ñ½Å Ö Â¹Ñ½Å Ö Ê À Ò³ [18] ¼ Ö Ñ½ Ö Üà Û¹ ѽ Õ Ö ÜÃ Ì ÅÛ ÏÃ Ò Å Ö Ä Ò³ Ñ ½ Æ»ÏÒ Ö ÙÃ Ñ½Å»Ï Æ Ú 1a SAZ ÔÏ Æ Ú 1e À Æ ÝÖ Ã ¹» Û Õ Ä Óß ß Ä Óµ Ý ¼» Ê Ê ¹ Â Ø ÊÎÊÉ» ÅÅ ÝÒÌÖ Ã Ø ÛÈ º Î Ö ÝÃ Õ È 3.1. Â Ä Á Ê ½ Ê Ò ÕÈ Ó Æ Õ Ê Û Â Ê È Û ¾ È» ÆÏ Ý Á Û ÈÝÆÏ Ý Õ Û Èϳ Ë È ÑÓ Å Al-Cu-Mg Ê Ø Al Cu (θ ) ± Al CuMg(S ) ß À«θ S Ð Ø Ê Cu Õ ± Cu:Mg ¹ºÆØ Ó 04 ½ Ê Cu Õ 4.4 mass% Cu:Mg.8 Õ Al-Cu-Mg ÊÁ½ Ú Õ ±¹º Ê Ñ S Õ θ Ú 04 ½ Ê BM ±Ö (NZ) XRD ÄÐ θ ± ¼ (111) (11) ± (041) S ³ θ ½ θ 4.07 Û Ë Ø Â Ã Ê θ Õ» ÏÄÐÝ [19] Ó ¼ S 04 ½ Ê BM µ»ò Ø ß Ê.7% È Î Ø «Í XRD ÄÐØ θ Õ Ô Ì Õ ÛÔÍ Ý È Ã ÊÖ Æ S 3. ÞÖ Ø ³ Ú 3 04 ½ Ê FSW ÀÕ Ó EXCO Óµ ± Ô² Ý Û EXCO 0.5 h Ö Ë

3 :hb+y B# 84 31s Fig.1 Microstructures on the top surface of the FSW AA04 joint (a) overview, (b) base metal, (c) HAZ, (d) TMAZ, (e) SAZ : Al Cu( ) : Al S CuMg( ) Intensity /a.u. : Al NZ BM / ~ R i : Al-Al 8 L ~ t w S $ : Al-Cu 8% Al-Mg 8 L ~ (? Y 8 S $ : Al $!q.w~ R i : w Al O # J 7X 4pf*O 8 o_[ )4 :o ~ ~ B+e % * B+_ n S 6 Æ+Z,$} [ n 7 v 3 : h SAZ Æ+ Z -p_~~\ka T+;[x BM HAZ { TMAZ B+KA;w4$o anv 3 : SAZ * _R6Te5 Æ+ + v : R\4 _Rqm$ R : 4q _R S $ W_=aN* #R S $-p_ ROP $ }[ h K 6 X _ RÆ+ # 8k q 4 R ^ : qm$ UB V - 04-T3 1~R im 0.3 V \d_rw B+ ^! S $y qm$ : wn 4 K 6 S $ O P 1 60 o Fig. XRD spectrum of BM and NZ of FSW AA04 3 ~ v *$Æ+ [ _ Æ+ ^! : S ${ _/ 1 ~ R i * 4 sw S $$! i E UB+ \d S $;_ Z#r O (v 3 : 0.5 h S $/ O V P [ ) 4 PU S $ Æ. #JFK$: k N Al Mg B +_ n : O ( *$A ;B+ } S $ : w 3.3 zri t v ~ R FSW H q 3 B S ~ ~ >8 Al Mg N O w EXCO ^ : n) TEM an L l d y ` BM(v 4a) HAZ S $ ; _ Cu I $ i sw Cu N B% ; # l 4 S $ U B+ : fm } p M (v 4e) { TMAZ (v 4f) ^ ^r w ' SAZ(v w 1 ~ R i ) S $ ; - L_ l # ' 4h) ^ H E ^ ^r. 1 5 µm i _ Z # *$ O!w # ;- Lsn S $ : v SAZ b "L^ ^ *$"F b B+B 8 ^. C $ Æ+ g Al *$ O ' i Al : O td? O 9 _? SCE SCE [0] )

4 4 z n : 04 SB M Ass?4 C C, [ o Æf? B+ knp#0bæ< FSW SAZ Æ+ Y =!-v (4a,e,f) {v h * BM ($ R $Y U M t y M ` Ll3F M ` (v 4a) ^PTF nm 0.95 nm nm w ' ^ Al CuMg(S $) 'y M ` (v 4b) ^ P TF nm nm nm w'0 ^ Al Cu (θ $) - E ) ~ R : q w S $' θ $$! n L ly 8 _ 4 b FSW HAZ { TMAZ ($ R k /m*$ " F 7wW_=8 * TMAZ 85 Fig.3 Corrosion behavior in the different regions during different corrosion periods of FSW AA04 (a) BM (b) HAZ (c) TMAZ-A (d) TMAZ-R (e) SAZ ($ R Y `_ ); # Y yk ~ ~\? 1_ot` ' SAZ ($ R *$ z U M `k A $ t)_ o' *uw v 8< rz ~ ~ # ;! SAZ B +8 R$H A_ o _8 S $ R *uw ( S $ F $ 4 SAZ Æ+ w (8 FSW S $ v 8< SAZ SAZ BX8 v 9 = "C$7Xm>B+ z) p' fm" SAZ TB+;Y V~d kn p S $ D Æ< FSW! SAZ B+;Y n'8h0 B rir?knqg _o >W_=/W8! BM ~~ SAZ sw? rh /m n'

5 :hb+y B# 86 31s Fig.4 TEM results of FSW AA04 on the top surface at different regions (a) (d) base metal, (e) HAZ, (f) TMAZ, (g) (i) SAZ [1] 0.0 FSW -AA Exothermic Heat flow /mw mg R^P ` ($ R L~v 3 B+8 an #0R^ `$ 4 ^4 B+ *$ v 4d,g 85 BM { SAZ : GPBZ GuinierPreston-Bagaryatshy zones 7 =!- * SAZ : #?`M fm GPBZ E $ # 3 F K ~ ~ t E $ ($ R *$ 7X #? R p$ w Kr H IF r it$ S $ > \W_=/W8 v ~R FSW Hq 3B BM HAZ % SAZ DSC 8 L l # 40 { 540. ` 5 R F ; p: R ; R 5 ; L ~ S $ ~ R )/nz : `? ' SSSα Cu-Mg R w p$ ~ GPBZ S ( IM \P) S $ S $ 8 ) v 5 : _R ; (; 50 v) GPBZ ; UVP` "_R5 ; (; 80 v) S $ S $ `; ( R ; (; ) ` 50 v S $ S $ ; (R5 ; (; ) ;. 80 v Uq Al-Cu-Mg ~R$v S $ $X II I IV 8.911(HAZ) (BM) -0.7 III -0.8 V 10.36(SAZ) o Temperature / C Fig.5 DSC thermograms of FSW AA04 on the top surface at different regions w 80 sn n5 ; S $ `; t [ _R ; (; 510 v) S $ ; p DSC # ) BM HAZ { SAZ S $ ` { T S $ `; B! { ( SAZ DSC # S $ `;. a ; B!v Mw BM { HAZ # J F = [ DSC 8 1 nz: SAZ tw$ S $ `

6 4 Ó Þ Ò : 04 ¾ĐË Å 87 lgi /A cm SAZ E SCE /V AA04 BM Al clad Fig.6 Potentiodynamic polarization behavior of FSW AA04 on the top surface at different regions in EXCO solution Table 1 Electrochemical data for different regions of FSW AA04 on the top surface in EXCO solution Regions E corr/v I corr/a cm Al clad Base metal Shoulder active zone ϳ SAZ S FSW Ò Ð Ú 6 04 ½ Ê FSW ÀÕ Ó EXCO 1 Ñ Á Ì Ó Í ß» Í Û Ð Å Í Å Ü Ä Ì Ü ÄÐ SAZ Í Å ¹ 04 ½ Ê Å V SCE SAZ Ì È Ø ¼ ¼ Ä Ê ± TEM Äе FSW Ö Ã É ¼ ß È ½ È ÈÎ ½ Û ¼ Û ½ ß È Ú Û ¼ Ä TEM ß DSC Äе FSW Ò SAZ S Û ĐÆ Mg ¾ SAZ Å Í Å Î 04 ½ Ê FSW Ö Ô Æ Ü Æ Õ S SAZ ¹ Ô Ã FSW Ö ½ ß È È Û Æ ÅÅ Æ 1 Óµ FSW Ò S Mg ĐÆ Å Í Å Æ ÒÞ ÙÏ Ó¾ S Ê SAZ ½ µæ ½Û Å Æ 3 Æ 1 ß 3 ¾ SAZ Ì ² 4 Æ (1) ÄÖ 04 ½ ÊÖ Ó Ì È ÔÆ Ü Æ Õ S () Ö Ã É ¼ ½ ß È Ú Û (3) ÄÖÒ ÙÏ Ó S Ê Óµ Ó¾Ô Ð µ ÙÏ S ½Û Ó Æ Û S ØÛ Mg ĐÆ Å Ó Ô EXCO Í ¹ 04 ½ Ê Å V SCE Ð ± [1] Matrukanitz R P. Selection and weldability of heattreatable aluminum alloys, ASM Handbook- Welding, Brazing and Soldering [M]. ASM Int., 1990: [] Thomas W M, Nicholas E D, Needham J C, et al. Friction stir butt welding [P]. Int. Pat., PCT/GB9/003, 1991, 9 [3] Ericsson M, Sandstrom R. Influence of welding speed on the fatigue of friction stir welds and comparison with MIG and TIG [J]. Int. J. Fatigue, 003, 5: [4] Su J Q, Nelson T W, Mishra R, et al. Microstructural investigation of friction stir welded 7050-T651 aluminum [J]. Acta Mater., 003, 51(3): [5] Omar H. Effects of peening on mechanical properties in friction stir welded 195 aluminum alloy joints [J]. Mater. Sci. Eng., 008, A49(1-): [6] Linton V M, Ripley M I. Influence of time on residual stresses in friction stir welds in age hardenable 7xxx aluminum alloys [J]. Acta Mater., 008, 56(16): [7] Li Y, Murr L E, McLure J C. Solid-state flow visualization in the friction-stir welding of 04 Al to 6061 Al [J]. Scr. Mater., 1999, 40(9): [8] Yan D Y, Shi Q Y, Wu A P, et al. Numerical analysis on the functions of stir tool s mechanical load during friction stir welding [J]. Acta Metall. Sin., 009, 45(8): (, ½ Ð,. ¾ Ý Æ ØÂÔ Õ» [J]. Ì ±, 009, 45(8): ) [9] Jariyaboon M, Davenport A J, Ambat R, et al. The effect of welding parameters on the corrosion behaviour of friction stir welded AA04-T351 [J]. Corros. Sci., 007, 49(): [10] Biallas G, Braun R, Donne C D, et al. Mechanical properties and corrosion behavior of friction stir welded 04-T3 [C]. 1st International Symposium on Friction Stir Welding, Thousand Oaks, CA, 1999 [11] Leonard A J. Corrosion resistance of friction stir welds in aluminum alloy 014A-T651 and 7075-T651 [A], 3rd International Symposium on Friction Stir Welding [C]. Kobe, Japan. 001 [1] Li J F, Zheng Z J, Zhang Z, et al. Electrochemical impedance spectroscopy of Al alloys during exfoliation corrosion [J]. J. Chin. Soc. Corros. Prot., 005, 5(1): 48-5

7 88 ݾŠ31 (, Ì,. Ì Ô ÐÑ [J]. º ±, 005, 5(1): 48-5) [13] Zhang D F, Tan X M, Ma L, et al. Aluminum pitting corrosion damage rule under service environment [J]. J. Chin. Soc. Corros. Prot., 010, 30(1): ( Þ, ¹À,. Ð Æ Ì ² º Ç [J]. º ±, 010, 30(1): 93-96) [14] Mishra R S, Ma Z Y. Friction stir welding and processing [J]. Mater. Sci. Eng., 005, R50: 1-78 [15] Pan C, Huang Y, Fu Q. A novel in-situ tracking approach for evaluating microstructural variations using SEM, EDS and EBSD and its applications in materials science [J]. Mod. Res. Educ. Topics Microsc., 007, [16] ASTM G Standard test method for exfoliation corrosion susceptibility in and 7 series aluminum alloys (EXCO Test) [S]. 007 [17] Habashi M, Bonte E, Galland J, et al. Quantitative measurements of the degree of exfoliation on aluminum alloys [J]. Corros. Sci., 1993, 35(1-4): [18] Fu R D, Luan G H, Dong C L, et al. Corrosion behavior of friction stir welded joint of 7075 aluminum alloy by acid salt spray [J]. Corros. Sci. Prot. Technol., 009, 1: (À,,. Ë Â 7075 Ì FSW  º [J]. º ¹, 009; 1: ) [19] Buchheit R G, Grant R P, Hlava P F, et al. Local dissolution phenomena associated with S phase (Al CuMg) particles in aluminum alloy 04-T3 [J]. J. Electrochem. Soc, 1997, 144(8): [0] Cheng Y L, Zhang Z, Cao F H, et al. Corrosion of LY1 aluminum alloy in sodium chloride solution [J]. Trans. Nonferrous Met. Soc. China, 003, 13(3): [1] Liu Z Y, Li Y T, Liu Y B, et al. Development of Al-Cu- Mg-Ag alloys [J]. Chin. J. Nonferrous Met., 007, 17(1): (º¾,, ºÉ. Al-Cu-Mg-Ag Ì ² Ç [J]. Ù Ì ±, 007, 17(1): ) CORROSION MECHANISM ON TOP SURFACE OF FRICTION STIR WELDED JOINT OF 04 ALUMINUM ALLOY KANG Ju 1, DONG Chunlin 1, LUAN Guohong 1, HE Miao 1, FU Ruidong 1. Beijing Aeronautical Manufacturing Technology Research Institute, China FSW Center, Beijing 10004;. State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao Abstract: In this paper, based on the analysis to surface microstructure of FSW AA04 joint, the corrosion evolution behavior was revealed by a quasi-in-situ observation method. Besides, the corrosion mechanism of the FSW joint was investigated by combining TEM, DSC and electrochemical analysis. The results show that FSW makes the corrosion resistance decrease, which is characterized by the facts that the most corrosion in the SAZ (shoulder active zone) and the pitting corrosion initially originates in dissolving of the S phase (Al CuMg). TEM observations indicate that crystal defects density increases in the welded joints causing the more different electrochemical properties between grains and grain boundaries. The S phase particles are broken and partially redissolved during the FSW process in the SAZ. When the corrosion happens, the broken S phase particles increase the pitting corrosion density of the SAZ. In addition, the activity of the SAZ is enhanced due to the doped Mg. Key words: friction stir welding, 04 aluminum alloy, microstructure, immersion test, second-phase precipitates