Vol.30 No Journal of Chinese Society for Corrosion and Protection Apr. 2010

Transcription

1 30 2 ¼Ê ÓÀ Vol.30 No Journal of Chinese Society for Corrosion and Protection Apr Mg 2 Si Ò Si Þ Al-Mg-Si ØÙÓ ÐÝ ÑÐ ÆÚ 1 1,2 BIRBILIS Nick 3 ± 1 ²³ 1,2 (1. ¾ ÁÈ ; 2. Ð ² ¾ ÁÈ» ÍÌ ; 3. ARC Centre of Excellence for Design in Light Metals, Department of Materials Engineering, Monash University, 3800 Australia) : Å Al-Mg-Si ²º ÊÄ ß Õ² Mg/Si Al-Mg-Si ²º ÊÄ (Al- Mg 2Si Al-Mg 2Si-Si) ß«Û Õ Æ Æ Î Mg/Si Al-Mg-Si ²ßº»É À Æ ³Ù º Si Å Al ß»É È ÎÆ Ù¾ Å Al ßßÎ ½ º Mg 2Si Å Al ß»ÉÎ ÎÆÎ ÀÎ ½ Þ Mg 2Si Ý Ö Mg ß Ü ½ Ý Ö Si ¾ Mg 2Si ¼ Å Al ß À Ø Ù¾ Å Al ßßÎ ½ Mg/Si>1.73 ß Al-Mg-Si ²º É ¹ß Mg Si ß º ÄÉ»É Ü ² ³± º»É Mg/Si<1.73 ß Al-Mg-Si ²º Æ Mg Si Si ÆÄ»É À Mg 2Si Ñ Si ÆÄ ÓÙ¾ Å Á ÒÄ ßÎ ½ Ó ÆØ Mg 2Si º Á Òß Ø µî Mg 2Si Å Á ÒßÎ ½»Éʺ Si ÆÄ Mg 2Si ÆÄ Åß Á Ò Si ÆÄ µî»éß Ù¾ ²³± Ä ßº»É º»É»É À Õ : Al-Mg-Si ² Ü : TG171 Å : A : Đ Al-Mg-Si ± 6 ± ž Ô ±«Í ÒØĐ À Ó«6 ± ÞÐºÈ«Ö ± Mg Si Ë Å«¹ Ã Þ ¹ ºÈºÈ º Đ «6 ± Mg/Si>1.73 ūžй Ï Mg 2 Si Åë± ¹ ºÈ º Mg/Si<1.73 ūžй Å Ï Mg 2 Si Åà Si ÅÃ«ÐºÈ «± ¹ ºÈ º [1] 2 Al-Cu-(Mg) 7 Al-Zn- Mg-(Cu) ±Í ÒØĐ ÐÀ «Ê ±ÞÐºÈ Þ ß «2 7 ±ÞºÈ ºÈ л Í ËÞž«µ ß «Í Ý ÐÈ Þ [2 8] Ö : Ô : à 1984 Á Ô Á Ç» ³ ½Ë : à lijinfeng@mail.cus.edu.cn 6 ±ºÈ Þž «² Ú ÛÞÌË ¼ µç «Ø Þ Ïß Þ ± Mg/Si>1.73 Þ 6 ± ¹ ºÈÞ Æ Mg/Si>1.73 Å«±¹ Ï Mg 2 Si Åë±ßÞ Mg 2 Si Åà «º Ƚ«Ø½ ± ¹ ºÈ º [9] Ì Birbilis Ð [10] ± Ô Ô Å ¾²Ø«Mg 2 Si 0.1M NaCl ¼ Þ «¾Đ ±ßÞÞ 6 ± NaCl ¼ Þ Æ V SCE «Mg 2 Si Þ Æ V SCE «Ê ³ Â Þ Đ 7 ±ßÞ ¹ ϵ MgZn 2 ³ Þ 7 ± 0.1M NaCl ¼ Þ Æ V SCE «MgZn 2 Þ Æ -1.1 V SCE [11] «6 ± Ϲ Ï Mg 2 Si Åà ± Mg/Si>1.73 Å «Ò Þ¹ ºÈ ºÒ Đ 7 ±Þ¹ ºÈÖ ÏĐß 6 ±Þ ÎÞ 6 ± ϵ Mg 2 Si Þ ß «³ ž 6 ±¹ Éõ

2 108 ÏºÈ Ò 30 ϵ Mg 2 Si Si ¹ ßÞ Þ Ô µ Ø Ô Þ «Å¾¹ Éõ Þ Ô «½ º Þ ºÈ ÞÈ «Ø Mg Si 6 ±ÞºÈÐ 2 Mg 2 Si ÞÔ Ã³«ØƵ Ò Ð Ý ±Þ Mg 2 Si Ý Mg 2 Si Þ 2Æ1 ÞÜ Â³ ËÞ Mg Si ÝÛ Ï Ã ÐÞÏÆ Þ Ò Đ h Ò Ã Mg 2 Si Ô Ý Þ Mg 2 Si Ý XRD µ «Ð Mg 2 Si Ý MPa ÂÒÇ Ð Ã 10 min«ã Mg 2 Si Þ Àµ Mg 2 Si Àµ α(al) Si Þ ³Ï Æ«µÐØ Cu Ø³È «²ÀÍÒ Ñ ÀÍ ÒÅ Û» 1200 ¹«Cr 2 O 3 Ý Ë«Ò ÐÌ Ø Ø CHI660B Ô ÀÍ ³ Mg 2 Si α(al) Si Þ Ô±³«ºÈ 3.5% NaCl ¼ Ø Pt ¹ «Ñ ± ÊÞ Ã SCE Ô Æ 1 mv/s Mg 2 Si α(al) Si Éà Mg 2 Si-α(Al) Ñ 1 Mg 2 Si-α(Al)-Si ( 2) Þ «³ Ú Mg/Si>1.73 Mg/Si<1.73 Þ Al- Mg-Si ±¹ µéã«å¾ 3.5% NaCl ¼ Þ Ô Þ Mg 2 Si α(al) Si ÞÀÍ ÒĐ³ mm 2 24 mm mm 2 ÇÄË 312 h«ç µþ Ô Ð«Ø CHI660B Ô À Í ÐÞ Ô±³ Ø Sirion200 Ô ¼È ÞºÈ Mg/Si>1.73 Mg/Si<1.73 ÞÊ Al- Mg-Si ± ½«Ã³³ Al-0.63Mg-0.28Si (mass%) Al-0.63Mg-0.88Si (mass%) ±»Æ¼ Ò 175 /1 h Þž Ð ¹ ºÈÌË ¹ ÅÈÉ È ¹ ºÈÌË GB ±Á«ºÈ 3% NaCl+(36% 38%)HCl ¼ ²ÀÍÒØÄ Ñ «Ì ºÈ²Ò» ¹ Û Ë ßÐØ Ò ºÈ «Ø ¼½²Ò Þß «NaOH ¼ 10% ºÈ 5 min«³ïðøò ½«HNO 3 ¼»²Ò Ë «ÌÐØ Ò ½ Ò¾ <2d m 2 /L «ºÈ¼ ÐÄ ± Ï«µ± Æ 35 ±2 Þ Å 6 h ÌË Ð«³º³Ï Fig.1 Schematic diagram of coupling system of Mg 2Si -α(al) (a) planform, (b) cutaway view Fig.2 Planform of coupling system of Mg 2Si-α(Al)- Si Æ«µ Ò Û ËРż È ¹ º È Æ ¼ (TEM) È ÚØÏÆ» Û Ñ Ð Ñ 75%CH 3 OH+25% HNO 3 «Ø Tacnai G2 20 TEM È ¹ Þ ÏµÉà ³ 3 Ö ß Ê Mg/Si Þ Al-Mg-Si ±ÏÆ»¹ ºÈÌËÐ ÒºÈ 3 Æ «Mg/Si<1.73 Þ ±Ï À¹ ºÈ«Mg/Si>1.73 Þ ± Ï ¹ ºÈ ² ÝÚÞÌË ¼ ½Þ [1,9]» XRD ±ØÚ Þ Mg 2 Si Ý Õµ Mg 2 Si Ð Ð Ã Þ Mg 2 Si ÀµÞ Ô Õ Ì Mg 2 Si µþ Ô «ÝĐ ±ßÞÞ¹ À Ñ PFZ ±Ô Õ Ë «Å Ø α(al) Ó µç Ô Mg/Si<1.73 Þ 6 ±¹ ÏÞ Si ÅÃ Ø Si Ó Ô Þ

3 2  : Mg 2Si Si ÆÄ Al-Mg-Si ²º»É ÎÙ Àß Æ 109 Ý α Al Si Mg 2 Si 3.5% NaCl ¼ ÅÅÞ Ô±³ 4 µòþºè Ô Ð²²«Mg 2 Si ÞÆºÈ Ì¾«Si ÞÆºÈ Ì µò «Þ Ô È̽«Ð Þ Ô ÈÌ Å«Mg 2 Si µþæºè Ê µþæºè ÓØ«ÅÍ «Mg 2 Si Åà Si α(al) ¾ ºÈ Mg 2 Si-α(Al) Ñ Þ (Ú Mg/Si>1.73 Þ Al-Mg-Si ±¹ ÞµÉÃ) 3.5% NaCl ¼ Å 312 h Þ Ô±³ 5 «Mg 2 Si µþ ÝÍ Æ V(vs.SCE)»Æ V(vs.SCE)«Ø½ Mg 2 Si α(al) Þ «Mg 2 Si µ Þ Ý ĐÜ Õ Mg ÞÛ ¼ Ü Õ Si Þ ÚØ½Þ Ô 312 h Ð Mg 2 Si µþ ³ 6 ²Ø«µ Mg Õ Ë» %«Si Ë Â 68.13% 2 ± Ü ÕÛ ¼ «Ü Þ Õ Þ ¼ Buchhiet Ð [12] Shao Ð [13] Li Ð [14] Þž S µ (Al 2 CuMg) Þ 2 ±» NaCl ¼ ÅÐ«Ú S µ Ü Õ Mg Û ¼ «Cu Õ Þ ¼«µ S µ Mg 2 Si-α(Al) Þ Þ Ô Ø ½ Þ Ô ( 7)««ÝĐ Mg 2 Si ¾«Í Í «ÊÔÍ ÙÂ Å È «µ «Í µ Mg 2 Si-α(Al) Þ 3.5% NaCl ¼ Å 312 h ЫMg 2 Si α(al) ÞºÈ 8 Æ «²ÒºÈà «³ 6 ²Øµ Mg Table 1 Corrosion parameters of α (Al), Si and Mg 2Si at the beginning of corrosion in 3.5% NaCl solution. parameter E corr,sce/v I/ A cm 2 R P /Ω cm 2 α(al) Mg 2Si Si Fig.3 Metallographs of Al-Mg-Si alloys with different ratio of Mg/Si (a) Mg/Si<1.73, (b) Mg/Si>1.73 Fig.5 Potentiodynamic scanning curves of α(al) and Mg 2Si after coupling for 312 h in NaCl solution Si intensity /a.u. Mg Al Fig.4 Potentiodynamic scanning curves of individual α(al), Si and Mg 2Si at the beginning E /kev Fig.6 Energy spectrum of simulated bulk Mg 2Si phase in Mg 2Si-α(Al) coupled system after coupling for 312 h

4 110 ÏºÈ Ò 30 Fig.7 Coupling current of Mg 2Si with α(al) in 3.5% NaCl solution Fig.9 Potentiodynamic scanning curves of individual α(al), Si and Mg 2Si after coupling for 312 h in NaCl solution Fig.8 Corrosion morphologies of coupling system of Mg 2Si-α(Al) immersed in 3.5% NaCl solution for 312 h (a) α(al) (b) Mg 2Si º³¼ «²Ò Si Þ Ð ²Ò ºÈ Mg 2 Si-α(Al)-Si Þ (Ú Mg/Si<1.73 Þ Al-Mg-Si ±¹ ÞµÉÃ) 3.5% NaCl ¼ Å 312 h Þ Ô±³ 9 «Mg 2 Si α(al) Si ÐÞ Ï Í Ô«Si Þ ¹µ Ë Ì Mg 2 Si Þ «ÌÐؽ α(al) Þ Ì¾ ³ ²Ø«Mg 2 Si µ Ï ÍÜ Õ Mg ÞÛ ¼ Ü Õ Si Þ «Þ Mg 2 Si Þ Þ Si Mg 2 Si α(al) Þ Ô«ÏØ½Í Þ Ô«10a Ú «Si Þ ««Đ Mg 2 Si α(al) Þ «Þ Í «Ê Fig.10 Coupling current of Mg 2Si, Si and α(al) in the Mg 2Si-α(Al)-Si coupled system (a) comparison coupling current of Mg 2Si, Si and α(al), (b) coupling current of Mg 2Si-α(Al) at the intervals Ô Ç «α(al) Mg 2 Si Í Í «Mg 2 Si Í Í ÊÔ Í Ù Å È «Mg 2 Si «Mg 2 Si µ Ý α(al) «Mg 2 Si µþí µ α(al) Í Í ÊÔ Ù Å È «ÏÝĐ Mg 2 Si «Ø½ α(al) Ý Í «Í µ ÝĐ Þ Mg 2 Si α(al) Þ Ô«Ø½ Mg 2 Si -α(al)-si «Õ Mg 2 Si-α(Al) Þ «Mg 2 Si Ý Í ÞÊÔÍ ÊÔ µ Þ «10b Ú

5 2  : Mg 2Si Si ÆÄ Al-Mg-Si ²º»É ÎÙ Àß Æ Ú Þ 3.5% NaCl ¼ Å 312 h ЫMg 2 Si α(al) ÞºÈ Ï «Mg 2 Si ²Ò Í Ã ÞºÈ«α(Al) ²ÒºÈÇÆ Mg 2 Si-α(Al) Ñ Mg 2 Si-α(Al)-Si Þ «ÝĐ Mg 2 Si Úؽ Mg 2 Si α(al) Ô Þ Ç Ö Å «Æ 100 h Ð α(al) Þ Í 7 «Ð Æ 50 h Ð α(al) Þ Í 10 «µ ³ «Ð α(al) ÞºÈÇÆ «ÝĐ Þ Si «Ò ؽ α(al) ÞÍ ¼ «Ò Mg 2 Si Mg ÞÛ ¼ «α(al) º Í ÔÞ Ç Ø Si Åà ±ºÈ ÞÍثػ Þ Í Al-10%Si ± 12 Al-10%Si ± 3.5% NaCl ¼ Å 3 d ÐÞ SEM «Å ±» Íà ޺ȫºÈ Si µ Þ Al ßÞ «ÓØ Si µí Í Al ßÞÞºÈ Ò Ô ÌË «Mg/Si Al-Mg-Si ±¹ ÅÈÉ «ÝÏ 14 Ú Þ Mg/Si Al-Mg-Si ±ºÈÐ Mg/Si>1.73 Å«Al-Mg-Si ±¹ È ³ Þ Mg 2 Si Åà ( 14a) ÝĐ Mg 2 Si ¾«º È Đ¹ Mg 2 Si ЫÝĐ Mg 2 Si Ü Õ Mg ÞÛ ¼ Ü Õ Si Þ «Mg 2 Si «Ø½ À ÑÞÍ ¼ ºÈ µ ÝĐ¹ Mg 2 Si ³ È «¹ ÃÈ ÞºÈĐÛ«Ï Mg/Si>1.73 Þ Al-Mg -Si ± ¹ ºÈ º 13a Mg/Si<1.73 Å«Al-Mg-Si ±¹ È ³ Þ Mg 2 Si ÅÃ«Å Ï ÃÞ Si Åà ( 14b) ºÈÞÍ «ÝĐ Mg 2 Si Þ Ì¾«ºÈ Đ Mg 2 Si µ²ò й ÝĐ Þ Si ÅÃÞ «Òؽ Si Åà À Ñ ÞÍ ¼ «Ò Mg 2 Si Ü Õ Mg Þ Û ¼ Ü Õ Si Þ «Í Mg 2 Si ßÞÞ Ç«Í Mg 2 Si À ÑÞÍ ¼ Mg/Si<1.73 Þ Al- Mg-Si ±¹ ºÈ Đ Mg 2 Si µ«é¹ À Ñ «Ï Mg/Si<1.73 Þ Al-Mg-Si ±¹ ϵ È «ÝĐ Si Åà À ÑÞ ºÈ«µ Mg 2 Si À Ñ޺ȫFig.12 Corrosion morphology of a Al-10%Si alloy immersed in 3.5% NaCl solution for 3 d Fig.11 Corrosion morphologies of coupling system of Mg 2Si-α(Al)-Si immersed in 3.5% NaCl solution for 312 h (a) α(al), (b)mg 2Si Fig.13 Schematic diagram of function mechanism of Mg 2Si and Si precipitate in intergranular corrosion of Al-Mg-Si alloys (a) Mg/Si>1.73, (b) Mg/Si<1.73

6 112 ÏºÈ Ò 30 Fig.14 TEM micrographs in the area of grain boundary of Al-Mg-Si alloys with different ratios of Mg to Si (a) Mg/Si>1.73, (b) Mg/Si<1.73 Õؽ ¹ ÃÈ ºÈĐÛ«Ï ± ¹ ºÈ º 13b 4 Öß (1) Al-Mg-Si ±ºÈÍ «¹ Mg 2 Si ±ßÞ¾«Í Í Û Í ¼ ºÈ ЫÝĐ Mg 2 Si Ü Õ Mg ÞÛ ¼ «Þ Ü Õ Si «ÏÝ Mg 2 Si Þ µ «Ø½ ßÞÞÍ ¼ ºÈ (2) Mg/Si>1.73 Þ Al-Mg-Si ±¹ ϵ È «¹ ÃÈ ºÈĐÛ«± ² Ï ¹ ºÈÖ (3) Mg/Si<1.73 Þ Al-Mg-Si ±¹ Í ÏÍ Mg Si ϵ «Ö ÏÍÌ Þ Si Å ºÈÍ «ÝĐ Mg 2 Si Þ Ì¾«ºÈ Đ Mg 2 Si µ²ò Ùй ÝĐ Þ Si Å ÃÞ «Òؽ Si Åà À ÑÞÍ ¼ «Ò Mg 2 Si Ü Õ Mg ÞÛ ¼ Ü Õ Si Þ «Í Mg 2 Si ß ÞÞ Ç«Í Mg 2 Si À ÑÞÍ ¼ Û «[1] Osaki S H, Kinoshita K, Naganuma D. Intergranular corrosion and SCC properties of Al-Mg-Si alloy sheets [J]. J. Inst. Light Met., 2003, 53(4): [2] Es-Said O S, Frazier W E, Lee E W. The effect of retrogression and reaging on the properties of the 7249 aluminum alloy [J]. JOM. 2003, (1): [3] Zheng Z Q, Li H Y, Mo Z M. Retrogression and reaging treatment of a 7055 type aluminum alloy [J]. Chin. J. Nonferrous Met., 2001, 11(5): ( Å, à Ñ, ÞºÕ ³ RRA Á [J]. ³ Á, 2001, 11(5): ) [4] Ru J G, Yi L N,Zhang L S. A study of the ultra high strength aluminium alloy heat treatment process [J]. J. Mater Eng., 1999, (2): (,,. ³ ÁÂ Ç [J]. ÂÉ, 1999, (2): 37-39) [5] Pzark J K, Ardell A J. Microstructures of the commercial 7075 Al, alloy in the T651 and T7 tempers [J]. Metall. Trans., 1983, 14: [6] Meng Z F, Zheng Y, Long H W, et al, Hardness changes of Al-Zn-Mg alloy during retrogression and reaging [J]. Acta Metall. Sin., 1997, 33(5): (Ð,, Đ. Ç - ÙÎ - Ç Á É Al-Zn-Mg ³Ô [J]. ³ Á, 1997, 33(5): ) [7] Zeng Y, Yin Z M, Zhu Y Z, et al. Effect of RRA on microstructure and properties of new type ultra high strength aluminum alloy [J]. Chin. J. Nonferrous Met., 2004, 14(7): (, кÕ, ºĐ. RRA Á ³«ÉË µ Ó¹ [J]. ³ Á, 2004, 14(7): ) [8] Li J F, Peng Z W, Li C X, et al. Mechanical properties, corrosion behaviors and microstructures of 7075 aluminium ally with various aging treatements [J]. Trans. Nonferrous Met. Soc. China, 2008, 18: [9] Wang Z T, Tian R Z. Handbook of Aluminum Alloy and Fabrication (2nd) [M]. ChangSha: Central South University Press, 2000: 132 ( Ü, º. ³  Å[M]. ĐÐÁ ) [10] Birbilis N, Buchheit R G. Electrochemical characteristics of intermetallic phases in aluminum alloys [J]. J. Electrochem. Soc., 2005, 152(4), B140-B151 [11] Li J F, Zheng Z Q, Li S C, et al. Simulation study on function mechanism of some precipitates in localized corrosion of Al alloys [J]. Corros. Sci., 2007, 49: [12] Buchheit R G, Grant R P, Hlava P F, et al. Local dissolution phenomena associated with S phase(al 2 CuMg) particles in aluminum alloy 2024-T3 [J]. J. Electrochem. Soc., 1997, 144(8): [13] Shao M H, Fu Y, Hu R G, et al. A study on pitting corrosion of aluminum alloy 2024-T3 by scanning microref-

7 2  : Mg 2Si Si ÆÄ Al-Mg-Si ²º»É ÎÙ Àß Æ 113 erence electrode technique [J]. Mater. Sci. Eng., 2003, A344: [14] Li J F, Zheng Z Q, Jiang N, et al. Study on localized corrosion mechanism of 2 series Al alloy containing S(Al 2 CuMg) and θ (Al 2 Cu) precipitates in 4.0% NaCl solution at ph=6.1 [J]. Mater. Chem. Phys., 2005, 91(2-3): [15] Mizuno K, Nylund A, Olefjord I. Surface reactions during pickling of an aluminum-magnesium-silicon alloy in phosphoric acid [J]. Corros. Sci., 2001, 43(2): [16] Li J F, Zheng Z Q, Ren W D, et al. Simulation on function mechanism of T1(Al 2 CuLi) precipitate in localized corrosion of Al-Cu-Li alloys [J]. Trans. Nonferrous Met. Soc. China, 2006, 16: [17] Wang Z H, Zhou G Y. Controlling composition of 6063 aluminium alloy based on production process and material application [J]. Light Alloy Fabr. Technol., 2000, (12): ( Ç, ÌÖ. Â Ú 6063 ³ Å µ [J]. ³ «, 2000, (12): SYNERGETIC EFFECT OF Mg 2 Si AND Si PARTICLES ON INTERGRANULAR CORROSION OF Al-Mg-Si ALLOYS THROUGH MULTI-ELECTRODE COUPLING SYSTEM LI Chaoxing 1, LI Jinfeng 1,2, BIRBILIS Nick 3, JIA Zhiqiang 1, ZHENG Ziqiao 1,2 (1. School of Materials Science and Engineering, Central South University, Changsha ; 2. Key Laboratory of Nonferrous Metal, Materials Science and Engineering, Ministry of Education, Central South University, Changsha ; 3. ARC Centre of Excellence for Design in Light Metals, Department of Materials Engineering, Monash University, Australia) Abstract: The potentiodynamic scanning curves and the electrochemical coupling behaviors of constituent phases at the grain boundary of Al-Mg-Si alloy were investigated. The corrosion mechanism of Al-Mg-Si alloys different ratio of Mg to Si was analyzed. The results show that the Si particle is cathodic to the Al-base and causes the anodic dissolution of Al-base at its adjacent periphery. At the beginning, the precipitate of Mg 2 Si is anodic to the Al-base and corrosion occurs on its surface. However, during its corrosion process, its potential moves to a positive direction with immersion time increasing, due to the preferential dissolution of Mg and the enrichment of Si, which makes Mg 2 Si become cathodic to Al- base and leads to the anodic dissolution of the Al-base at its adjacent periphery at a later stage. At the grain boundary of Al-Mg-Si alloys with a ratio of Mg to Si higher than 1.73, the Mg-and-Si contained precipitates are distributed discontinuously, resulting in that they are not sensitive to intergranular corrosion. There exist Mg-and-Si-contained precipitates and Si particles at the grain boundary of Al-Mg-Si alloys with a ratio of Mg to Si less than 1.73, corrosion occurs firstly on the surface of Mg 2 Si. Meanwhile, the Si particle leads to the great anodic dissolution of the precipitate-free-zone(pfz) at its adjacent periphery. The Si particle also accelerates the preferential dissolution of Mg in Mg 2 Si precipitate, expediting the polarity transformation between Mg 2 Si and the PFZ. As a result, the corrosion development along the PFZ at the adjacent of Mg 2 Si particle is enhanced. Key words: Al-Mg-Si alloys, intergranular corrosion, corrosion mechanism