Key Microstructural Features Responsible for Improved Stress Corrosion Cracking Resistance and Weldability in 7xxx Series Al Alloys Containing Micro / Trace Alloying Additions


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The commercial 7xxx series Al alloys are based on medium strength Al-Zn-Mg and high strength Al-Zn-Mg-Cu systems. The medium strength alloys are weldable, whilst the high strength alloys are nonweldable. On the other hand, the Cu-free, weldable alloys suffer from poor SCC resistance. It is the purpose of this article to provide quantitative data and microstructural analysis to demonstrate that small additions of either Ag or Sc to Al-Zn-Mg and Al-Zn-Mg-Cu alloys bring about very significant improvement in SCC resistance and weldability, respectively. The improvement in SCC resistance of the Cu-bearing alloys due to over aging and retrogression and reaging (RRA) is further discussed in light of a similar improvement in the SCC resistance of these alloys, when peak aged, due to Ag and Sc additions.



Materials Science Forum (Volumes 519-521)

Edited by:

W.J. Poole, M.A. Wells and D.J. Lloyd




A.K. Mukhopadhyay et al., "Key Microstructural Features Responsible for Improved Stress Corrosion Cracking Resistance and Weldability in 7xxx Series Al Alloys Containing Micro / Trace Alloying Additions", Materials Science Forum, Vols. 519-521, pp. 315-320, 2006

Online since:

July 2006




[1] S.M. DeVincent, J.H. Devletian and S.A. Gedon: Welding Journal, Vol. 8 (1988), p.33.

[2] M.O. Speidel: Metall. Trans A, Vol. 6A (1975), p.631.

[3] A.W. Thompson: Mater. Sci. Engg., Vol. 43 (1980), p.41.

[4] T.J. Summerson and D.O. Sprowls: ICAA 1 (eds. E.A. Starke, Jr and T.H. Sanders, Jr. ), Vol. 3, p.1575 (EMAS, Warley, UK, 1986).

[5] T.D. Burleigh: Corrosion, Vol. 47 (1991), p.89.

[6] R.J. Gest and A.R. Troiano: Corrosion, Vol. 30 (1974), p.274.

[7] J. Albrecht, B.J. McTiernan, I.M. Bernstein and A.W. Thompson: Scr. Metall., Vol. 11 (1977), p.893.

[8] G.M. Scamans: J. Metal. Sci., Vol. 13 (1978), p.27.

[9] G.M. Scamans: Scripta Metall., Vol. 13 (1979), p.245.

[10] G.H. Koch: Corrosion, Vol. 35 (1979), p.73.

[11] G.M. Scamans: Aluminium, Vol. 58 (1982), p.332.

[12] W. Gruhl: Z. Metallkde, Vol. 75 (1984), p.819.

[13] J.R. Pickens and L. Christodoulou: Metall. Trans. A, Vol. 18A (1987), p.135.

[14] T. Magnin and P. Rieux: Scripta Metall, Vol. 21 (1987), p.907.

[15] J. Albrecht, I.M. Bernstein and A.W. Thompson: Metall. Trans A, Vol. 13 A (1982), p.811.

[16] A. Sendorek and A.W. Pearson: JIM, Vol. 99 (1971), p.33.

[17] T.H. Sanders, Jr. and E.A. Starke, Jr.: Metall. Trans. A, Vol. 7A (1976), p.1407.

[18] F.S. Lin and E.A. Starke, Jr.: Mater. Sci. Engg., Vol. 39 (1979), p.27.

[19] P. Doig, P.E.J. Flewitt and J.W. Edington: Corroison, Vol. 33 (1977), p.217.

[20] J. Busby, J.F. Cleave and R.L. Cudd: JIM, Vol. 99 (1975), p.41.

[21] B. Sarkar, M. Marek and E.A. Starke, Jr.: Metall. Trans. A, Vol. 12A (1981), p. (1939).

[22] S.C. Byrne: ICAA 1(eds.E.A. Starke, Jr. and T.H. Sanders, Jr. ), Vol. 2, p.1095(EMAS, Warley, UK, 1986).

[23] W. Gruhl and E. Wauschkuhn: JIM, Vol. 99 (1971), p.49.

[24] L. Christodoulou and H.M. Flower: Acta Metall., Vol. 28 (1980), p.481.

[25] B.M. Cina: US Patent 3, 856, 584 (1974).

[26] J.K. Park and A.J. Ardell: Metall. Mater. Trans. A, Vol. 15A (1984), p.1531.

[27] D.A. Lukasak and R.M. Hart: Light Metal Age, Vol. 10 (1991), p.11.

[28] Y. Arata, F. Matsuda, K. Nakata and K. Shinozaki: Trans. JWRI, Vol. 11 (1982), p.67.

[29] J.C. Lippold, E.F. Nippes and W.F. Savage: Welding Res. Supplt., Vol. 6 (1977), p.171.

[30] M.J. Dvornak, R.H. Frost and D.L. Olson: Welding Res. Supplt., Vol. 8 (1989), p.328.

[31] H.T. Kim, S.W. Nam, S.H. Hwang: J. Mater. Sci., Vol. 31 (1996), p.2859.

[32] C.E. Cross, W.T. Tack, L.W. Loechel and L.S. Kramer: Welding of Materials (eds.R.A. Patterson and K.U. Mahin), p.275 (ASM International, Materials Park, OH, 1990).

[33] ASTM-E-1681: ASTM Annual Book of Standards, 3. 02 (1995), p.992.

[34] B.D. Cullity: Elements of X-ray Diffraction (Addition-Wesley Publishing Company, USA, 1967).

[35] W.F. Savage and C.D. Ludin: Welding Res. Supplt., Vol. 5 (1965), p.433.

[36] P.P. Houldcroft: Brit. Weld. J., Vol. 2 (1955), p.471.

[37] K.S. Prasad, A.K. Mukhopadhyay and V.A. Joshi: Z. Metallkde., Vol. 95 (2004), p.1046.