Hostname: page-component-586b7cd67f-r5fsc Total loading time: 0 Render date: 2024-11-25T23:39:20.906Z Has data issue: false hasContentIssue false
  • English
  • Français

Mechanism of Etching of Al-4.5Mg-1.0Mn Alloy

Published online by Cambridge University Press:  26 July 2018

Aline D. Gabbardo ,
Xi Wang ,
Angeire Huggins  and
G. S. Frankel
Aline D. Gabbardo
Affiliation:
Fontana Corrosion Center, The Ohio State University, Columbus, OH 43210, USA
Xi Wang*
Affiliation:
Fontana Corrosion Center, The Ohio State University, Columbus, OH 43210, USA
Angeire Huggins
Affiliation:
Fontana Corrosion Center, The Ohio State University, Columbus, OH 43210, USA
G. S. Frankel
Affiliation:
Fontana Corrosion Center, The Ohio State University, Columbus, OH 43210, USA
*
*Author for correspondence: Xi Wang, E-mail: [email protected]
Get access

Abstract

5xxx series aluminum alloys, as Al-4.5Mg-1.0Mn (AA5083), are strengthened by Mg solid solution and work hardening. A drawback of this alloy is the fact that β phase, Al3Mg2, can precipitate on grain boundaries causing sensitization and intergranular corrosion, which is detrimental to the integrity of the structure. Metallography is an important technique to study the grain structure and highly sought for intergranular corrosion evaluation; however, revealing the grains of completely un-sensitized AA5083 is challenging. This paper introduces a new procedure to etch AA5083 samples that were solutionized at 450°C for 1.5 h. The new procedure is a two-step etching method, including a phosphoric acid pre-etching step and a Weck’s reagent coloring step. Solutionized, lightly sensitized, and as-received AA5083 were evaluated, and the grains were observed using optical microscopy. The microetching mechanism was further studied by optical profilometry, atomic force microscopy, scanning electron microscopy, and energy dispersive spectrometry. The phosphoric acid created a surface profile determined by the grain orientations and its reactivity, and the Weck’s reagent was then able to color grains by preferential MnO2 formation over some pre-etched grains. Moreover, the final polishing with colloidal silica was essential to reach a high contrast image.

Keywords

Aluminum alloycolor etchinggrain structurephosphoric acid etchingWeck’s reagent
Type
Materials Science Applications
Information
Microscopy and Microanalysis , Volume 24 , Issue 4 , August 2018 , pp. 374 - 386
Copyright
© Microscopy Society of America 2018 

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

ASTM, B928/B928M-15 (2015) Standard Specification for High Magnesium Aluminum-Alloy Products for Marine Service and Similar Environments. West Conshohocken, PA: ASTM International.Google Scholar
ASTM, E407-07 (2015) Standard Practice for Microetching Metals and Alloys. West Conshohocken, PA: ASTM International.Google Scholar
ASTM, G67-13 (2013) Standard Test Method for Determining the Susceptibility to Intergranular Corrosion of 5XXX Series Aluminum Alloys by Mass Loss after Exposure to Nitric Acid (NAMLT Test). West Conshohocken, PA: ASTM International.Google Scholar
Barker, L (1949) Revealing the grain structure of common aluminum alloy metallographic specimens. Trans Am Math Soc 42, 347–356.Google Scholar
Beraha, E Shpigler, B (1977) Color Metallography. Metals Park: American Society for Metals.Google Scholar
Bonyár, A Szabó, PJ (2012) Correlation between the grain orientation dependence of color etching and chemical etching. Microsc Microanal 18, 1389–1392.Google Scholar
Gao, L, Harada, Y Kumai, S (2012) Analysis of microstructure evolution and precise solid fraction evaluation of A356 aluminum alloy during partial re-melting by a color etching method. J Mater Sci 47, 6553–6564.Google Scholar
Gao, L, Harada, Y Kumai, S (2015 a) Microstructural characterization of aluminum alloys using Weck’s reagent, part I: Applications. Mater Charact 107, 426–433.Google Scholar
Gao, L, Harada, Y Kumai, S (2015 b) Microstructural characterization of aluminum alloys using Weck’s reagent, part II: Coloring mechanism. Mater. Charact 107, 434–452.Google Scholar
Goswami, R, Spanos, G, Pao, PS Holtz, RL (2011) Microstructual evolution and stress corrosion cracking behavior of Al-5083. Metall Mater Trans A 42A, 348–355.Google Scholar
Graff, WR Sargent, DC (1981) A new grain-boundary etchant for aluminum alloys. Metallography 14, 69–72.Google Scholar
Kulinich, SA, Akhtar, AS, Wong, PC, Wong, KC Mitchell, KA (2007) Growth of permanganate conversion coating on 2024-Al alloy. Thin Solid Films 515, 8386–8392.Google Scholar
Lim, M, Scully, J Kelly, R (2013) Intergranular corrosion penetration in an Al-Mg alloy as a function of electrochemical and metallurgical conditions. Corrosion 69(1), 35–47.Google Scholar
McMahon, ME, Steiner, PJ, Lass, AB Burns, JT (2017) The effect of temper and composition on the stress corrosion cracking of Al-Mg alloys. Corrosion 73(4), 347–361.Google Scholar
Mohammadtaheri, M (2012) A new metallographic technique for revealing grain boundaries in aluminum alloys. Metallogr Microstruct Anal 1(5), 224–226.Google Scholar
Pourbaix, M (1966) Atlas of Electrochemical Equibria in Aqueous Solutions. New York, NY: Pergamon.Google Scholar
Prapasajchavet, K, Harada, Y Kumai, S (2017) Microstrucure Analysis of Al–5.5at%Mg Alloy Semi-Solid Slurry by Weck’s Reagent. Int J Metalcast 11(1), 123–130.Google Scholar
Rasband, WS (1997–2016) Image J. Bethesda, MD: US National Institutes of Health. Available at https://imagej.nih.gov/ij/ (retrieved June 19, 2017).Google Scholar
Searles, JL, Gouma, PI Buchheit, RG (2001) Stress corrosion cracking of sensitized AA5083 (Al-4.5Mg-1.0Mn). Metall Mater Trans A 32A, 2859–2867.Google Scholar
Seong, J, Yang, F, Scheltens, F, Frankel, GS Sridhar, N (2015) Influence of the Altered Surface Layer on the Corrosion of AA5083. J Electrochem Soc 162(6), C209–C218.Google Scholar
Suárez-Peña, B, Asensio-Lozano, J Vander-Voort, GF (2010) Colour metallography in commercial Al-Si alloys. Optimization of the microstructural characterization techniques in light optical microscopy. Rev Metal 46(5), 469–476.Google Scholar
Szabó, PJ Bonyár, A (2012) Effect of grain orientation on chemical etching. Micron 43, 349–351.Google Scholar
Szabó, PJ Kardos, I (2010) Correlation between grain orientation and the shade of color etching. Mater Charact 61, 814–817.Google Scholar
Vander Voort, GF (1984) Metallography Principles and Practice. New York, NY: McGraw-Hill.Google Scholar
Vander Voort, GF (2004) Color metallography. In: ASM Handbook Volume 9: Metallography and Microstructures, Vander Voort GF, pp. 493–512. Metals Park, OH: ASM International.Google Scholar
Weck, E Leistner, E (1986) Metallographic Instructions for Colour Etching by Immersion Part III: Non-Ferrous Metals, Cemented Carbides and Ferrous Metals, Nickel-Base and Cobalt-Base Alloys. Düsseldorf: Deutscher Verlag fur Schweibtechnik.Google Scholar
Wong, D, Swett, L Cocks, F (1979) Aluminum corrosion in uninhibited ethylene glycol‐water solutions. J Electrochem Soc 126(1), 11–15.Google Scholar
Yang, HS (1997) A new light optical metallographic technique for revealing grain structures of common 2000, 5000, and 7000 series aluminum alloys. Mater Charact 38, 165–175.Google Scholar
Zhang, R, Gupta, RK, Davies, CH, Hodge, AM, Tort, M Xia, K, et al. (2016) February). The influence of grain size and grain orientation on sensitization in AA5083. Corrosion 72(2), 160–168.Google Scholar
Zhang, X, Cen, X, Ravichandran, R, Hughes, LA Benthem, K. v. (2016) Simultaneous scanning electron microscope imaging of topographical and chemical contrast using in-lens, in-column, and Everhart–Thornley detector systems. Microsc Microanal 22, 565–575.Google Scholar
Zhu, Y (2012) Characterization of Beta Phase Growth and Experimental Validation of Long Thermal Exposure Sensitization of AA5xxx Alloys. Master thesis. Salt Lake City: University of Utah.Google Scholar
Zhu, Y, Cullen, DA, Kar, S, Free, ML Allard, LF (2012) Evaluation of Al3Mg2 precipitates and Mn-rich phase in aluminum-magnesium alloy based on scanning transmission electron microscopy imaging. Metall Mater Trans A 43A, 4933–4939.Google Scholar
Zwieg, T (2001) A universal method of mechanical preparation for producing sharply edged specimens and the colour etching of aluminum alloys. Prakt Metallogr 38(2), 63–73.Google Scholar