Pitting Corrosion in AA7075 Friction Stir Welds on Minor Additions of Silver


  • Kodamasimham Sri Ram Vikas Kodamasimham
  • Venkata Ramana Vuppala Sesha Narasimha Department of Mechanical Engineering, GITAM (Deemed to be University), Visakhapatnam 530045, Andhra Pradesh, India
  • Koona Bhavani Department of Mechanical Engineering, GITAM (Deemed to be University), Visakhapatnam 530045, Andhra Pradesh, India
  • Challa Kishore Reddy Department of Mechanical Engineering, Prasad V. Potluri Siddhartha Institute of Technology, Vijayawada 520007, Andhra Pradesh, India
  • Vadapalli Srinivas Department of Mechanical Engineering, GITAM (Deemed to be University), Visakhapatnam 530045, Andhra Pradesh, India




AA7075 is extensively used in aerospace, defense, automotive applications because of its high strength to weight ratio. Issues related to fusion welding and corrosion resistance are key problems associated with these alloys. Friction stir welding is an alternative welding technique that overcomes problems associated with fusion welding. In the present investigation, preliminary studies were done on pitting corrosion behavior of AA7075 friction stir welds by adding silver along the weld joint line. Silver paste was applied along the longitudinal direction of AA7075-T6 rolled plates of 6-mm thickness and cured at 130 C for 30 seconds. Weld joints were prepared at two different tools rotational speeds, i.e., 750 rpm and 1000 rpm, while keeping other parameters fixed. Welded joints were cut as per the required sizes to study the hardness, microstructure, and pitting corrosion resistance in various regions. It was observed that the hardness was not much affected, but pitting corrosion resistance substantially improved by trace addition of silver. In the stir zone and the thermo-mechanically affected zone, onion ring type marks were observed. Grain refinement in the stirred zone (SZ) was higher at 750 rpm compared to 1000 rpm. The increased hardness in the welds was due to grain refinement. All the observed results were correlated with microstructural features as evidenced by optical microscopy.


Staley, J.T., History of Wrought-Aluminum-Alloy Development, Aluminum Alloys-Contemporary Research and Applications, 31, Elsevier, pp. 3-31, 1989.

Nicolas, M. & Deschamps, A., Characterisation and Modelling of Precipitate Evolution in an Al?Zn?Mg Alloy During Non-Isothermal Heat Treatments, Acta Mater., 51(20), pp. 6077-6094, Dec. 2003.

Alatorre, N., Ambriz, R.R., Noureddine, B., Amrouche, A., Talha, A. & Jaramillo, D., Tensile Properties and Fusion Zone Hardening for GMAW and MIEA Welds of a 7075-T651 Aluminum Alloy, Acta Metall. Sin. English Lett., 27(4), pp. 694-704, Jul. 2014.

Venugopal, T, Roa. K.S. & Roa, K.P., Studies on Friction Stir Welded AA 7075 Aluminium Alloy, Trans. Indian Inst. Met., 57(6), pp. 559-663, 2004.

John, R., Jata, K.V. & Sadananda, K., Residual Stress Effects on Near-threshold Fatigue Crack Growth in Friction Stir Welds in Aerospace Alloys, in International Journal of Fatigue, 2003, 25(9-11), pp. 939-948, 2003

Sameljuk, A., Neikov, O., Krajnikov, A., Milman, Y. & Thompson, G., Corrosion Behaviour of Powder Metallurgical and Cast Al?Zn?Mg Base Alloys, Corros. Sci., 46(1), pp. 147-158, Jan. 2004.

Doig, P. & Edington, J.W., Influence of Precipitate Free Zones on the Stress Corrosion Susceptibility of a Ternary Al-5.9 Wt% Zn-3.2 Wt% Mg Alloy, Corrosion, 31(10), pp. 347-352, Oct. 1975.

Shikama, T. & Yoshihara, S., Highly SCC Resistant 7000-series Aluminum Alloy Extrusion, Kobelco Technol. Rev., 35, pp. 65-68, 2017.

Shastry, C.R., Levy, M. & Joshi, A., The Effect of Solution Treatment Temperature on Stress Corrosion Susceptibility of 7075 Aluminium Alloy, Corros. Sci., 21(9-10), pp. 673-688, Jan. 1981.

Yang, W., Ji, S., Zhang, Q. & Wang, M., Investigation of Mechanical and Corrosion Properties of an Al-Zn-Mg-Cu Alloy under Various Ageing Conditions and Interface Analysis of ?? Precipitate, Mater. Des., 85, pp. 752-761, Nov. 2015.

Kumar, P.V., Reddy, G.M. & Rao, K.S., Microstructure, Mechanical and Corrosion Behavior of High Strength AA7075 Aluminium Alloy Friction Stir Welds ? Effect of Post Weld Heat Treatment, Def. Technol., 11(4), pp. 362-369, Dec. 2015.

Vijaya Kumar, P., Madhusudhan Reddy, G. & Srinivasa Rao, K., 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, Def. Technol., 11(2), pp. 166-173, Jun. 2015.

Kumar, S., Kumar, A. & Vanitha, C., Corrosion Behaviour of Al 7075 /Tic Composites Processed Through Friction Stir Processing, Mater. Today Proc., 15, pp. 21-29, 2019.

Ikumapayi, O.M. & Akinlabi, E.T., Efficacy of ?-? Grade Titanium Alloy Powder (Ti?6Al?2Sn?2Zr?2Mo?2Cr?0.25Si) in Surface Modification and Corrosion Mitigation in 3.5% Nacl on Friction Stir Processed Armour Grade 7075-T651 Aluminum Alloys - Insight in Defence Applications, Mater. Res. Express, 6(7), 076546, Apr. 2019.

Riveros, V., Influence of Surface Treatments in the Initial Stages of Anodizing Al?Ag Alloys in Neutral Electrolytes, J. Solid State Electrochem., 10(2), pp. 83-90, Feb. 2006.

Paez, M.A., Anodic Oxidation of Al-Ag Alloys, Corros. Sci., 44(12), pp. 2857-2863, Dec. 2002.

Afzali, P., Yousefpour, M. & Borhani, E., Evaluation of the Effect of Ageing Heat Treatment on Corrosion Resistance of Al-Ag Alloy Using Electrochemical Methods, J. Mater. Res., 31(16), pp. 2457-2464, Aug. 2016.

Hatch, J.E., Aluminum: Properties and Physical Metallurgy, American Society for Metals, 1984.

Polmear, I.J., The Influence of Small Additions of Silver on the Structure and Properties of Aged Aluminum Alloys, JOM, 20(6), pp. 44-51, Jun. 1968.

Ogura, T., Hirosawa, S., Hirose, A. & Sato, T., Effects of Microalloying Tin and Combined Addition of Silver and Tin on the Formation of Precipitate Free Zones and Mechanical Properties in Al-Zn-Mg Alloys, Mater. Trans., 52(5), pp. 900-905, May 2011.

Hirano, M., Kobayasi, K. & Tonda, H., Effect of the Chemical Composition on the Mechanical Properties and Stress Corrosion Cracking Sensitivities of High-Strength Al-Zn-Mg Alloy, J. Soc. Mater. Sci. Japan, 49(1), pp. 86-91, 2000.

Mondolfo, L.F., Aluminum Alloys: Structure and Properties, London: Butterworths, 1976.

Hirano, M., Kobayasi, K. & Tonda, H., Effect of the Additional Element on the Weldability of High-Strength Al-Zn-Mg Alloy, J. Soc. Mater. Sci. Japan, 49(1), pp. 92-97, 2000.

Isadare, A.D., Effect of Heat Treatment on Some Mechanical Properties of 7075 Aluminium Alloy, Materials Research, 16(1), pp. 190-194, 2013.

Lotfi, Amir, H. & Nourouzi, S., Effect of Welding Parameters on Microstructure, Thermal, And Mechanical Properties of Friction-Stir Welded Joints of AA7075-T6 Aluminum Alloy, Metallurgical and Materials Transactions A, 45(6), pp. 2792-2807, 2014.

Sudhakar, I., Enhancement of Wear and Ballistic Resistance of Armour Grade AA7075 Aluminium Alloy Using Friction Stir Processing, Defence Technology, 11(1), pp. 10-17, 2015.

Rezaei, H., Mirbeik, M.H. & Bisadi, H., Effect of Rotational Speeds on Microstructure and Mechanical Properties of Friction Stir-Welded 7075-T6 Aluminium Alloy, Proc. Inst. Mech. Eng. Part C J. Mech. Eng. Sci., 225(8), pp. 1761-1773, 2011.

Golezani, A.S., Barenji, R.V., Heidarzadeh, A. & Pouraliakbar, H., Elucidating of Tool Rotational Speed in Friction Stir Welding of 7020-T6 Aluminum Alloy, Int. J. Adv. Manuf. Technol., 81(5-8), pp. 1155-1164, Nov. 2015.

Linton, V.M. & Ripley, M.I., Influence of Time on Residual Stresses in Friction Stir Welds in Agehardenable 7xxx Aluminium Alloys, Acta Mater., 56(16), pp. 4319-4327, Sep. 2008.

Rajakumar, S., Muralidharan, C. & Balasubramanian, V., Influence of Friction Stir Welding Process and Tool Parameters on Strength Properties of AA7075-T6 Aluminium Alloy Joints, Mater. Des., 32(2), pp. 535-549, Feb. 2011.

Dehghani, K., Ghorbani, R. & Soltanipoor, A.R., Microstructural Evolution and Mechanical Properties During The Friction Stir Welding of 7075-O Aluminum Alloy, Int. J. Adv. Manuf. Technol., 77(9-12), pp. 1671-1679, Apr. 2015.

Maitra, S. & English, G.C., Mechanism of Localized Corrosion of 7075 Alloy Plate, Metall. Trans. A, 12(3), pp. 535-541, Mar. 1981.

Rao, T.S., Reddy, G.M. & Rao, S.R.K., Microstructure and Mechanical Properties of Friction Stir Welded AA7075?T651 Aluminum Alloy Thick Plates, Trans. Nonferrous Met. Soc. China, 25(6), pp. 1770-1778, Jun. 2015.

Mehri, A., Abdollah-zadeh, A., Habibi, N., Hajian, M. & Wang, J.T., The Effects of Rotational Speed on Microstructure and Mechanical Properties of Friction Stir-Welded 7075-T6 Thin Sheet, J. Mater. Eng. Perform., 29(4), pp. 2316-2323, Apr. 2020.

Tian, W., Li, S., Wang, B., Liu, J. & Yu, M., Pitting Corrosion of Naturally Aged AA 7075 Aluminum Alloys with Bimodal Grain Size, Corros. Sci., 113, pp. 1-16, Dec. 2016.

Heydarian, A. Dehghani, K. & Slamkish, T., Optimizing Powder Distribution in Production of Surface Nano-Composite via Friction Stir Processing, Metall. Mater. Trans. B, 45(3), pp. 821-826, Jun. 2014.

Tabasi, M., Farahani, M., Givi, M.K.B., Farzami, M. & Moharami, A., Dissimilar Friction Stir Welding of 7075 Aluminum Alloy to AZ31 Magnesium Alloy Using Sic Nanoparticles, Int. J. Adv. Manuf. Technol., 86(1-4), pp. 705-715, Sep. 2016.