Aluminium–zinc alloys

Aluminium brass is a technically rather uncommon term for high-strength and partly seawater-resistant copper-zinc cast and wrought alloys with 55–66% copper, up to 7% aluminium, up to 4.5% iron, and 5% manganese. Aluminium bronze is technically correct as bronze, a zinc-free copper-tin casting alloy with aluminium content.

The term "special brass" is much more common for this, which then also includes alloys that add further characteristic elements to the copper-zinc base. In addition to the already mentioned elements of iron and manganese, lead, nickel and silicon can also be found as alloy components.

Due to their aluminium content, which is susceptible to oxidation at the usual melting temperatures in the range of 900 °C, the alloys require careful melting and melting treatment. Even when potting, attention must be paid to any oxides forming.

7000 series

7000 series are alloyed with zinc, and can be precipitation hardened to the highest strengths of any aluminium alloy. Most 7000 series alloys include magnesium and copper as well.

7000 series aluminium alloy nominal composition (% weight) and applications
Alloy Al contents Alloying elements Uses and refs
7005 93.3 Zn 4.5; Mg 1.4; Mn 0.45; Cr 0.13; Zr 0.14; Ti 0.04 Extrusions
7010 93.3 Zn 6.2; Mg 2.35; Cu 1.7; Zr 0.1; Aerospace
7022 91.1 Zn 4.7; Mg 3.1; Mn 0.2; Cu 0.7; Cr 0.2; plate, molds[1][2]
7034 85.7 Zn 11.0; Mg 2.3; Cu 1.0 Ultimate tensile strength 750 MPa[3]
7039 92.3 Zn 4.0; Mg 3.3; Mn 0.2; Cr 0.2 Aerospace armour plate
7049 88.1 Zn 7.7; Mg 2.45; Cu 1.6; Cr 0.15 Universal, aerospace
7050 89.0 Zn 6.2; Mg 2.3; Cu 2.3; Zr 0.1 Universal, aerospace
7055 87.2 Zn 8.0; Mg 2.3; Cu 2.3; Zr 0.1 Plate, extrusions, aerospace[4]
7065 88.5 Zn 7.7; Mg 1.6; Cu 2.1; Zr 0.1 Plate, aerospace[5]
7068 87.6 Zn 7.8; Mg 2.5; Cu 2.0; Zr 0.12 Aerospace, Ultimate tensile strength 710 MPa
7072 99.0 Zn 1.0 Sheet, foil
7075 & 7175 90.0 Zn 5.6; Mg 2.5; Cu 1.6; Cr 0.23 Universal, aerospace, forgings
7079 91.4 Zn 4.3; Mg 3.3; Cu 0.6; Mn 0.2; Cr 0.15 –
7085 89.4 Zn 7.5; Mg 1.5; Cu 1.6 Thick plate, aerospace[6]
7090 Al-Zn-Mg-Cu with Co 1.5% high strength, ductility and resistance to stress corrosion cracking[7]
7091 Al-Zn-Mg-Cu with Co 0.4% high strength, ductility and resistance to stress corrosion cracking[7]
7093 86.7 Zn 9.0; Mg 2.5; Cu 1.5; O 0.2; Zr 0.1 Aerospace
7116 93.7 Zn 4.5; Mg 1; Cu 0.8 Heat-treatable
7129 93.2 Zn 4.5; Mg 1.6; Cu 0.7 –
7150 89.05 Zn 6.4; Mg 2.35; Cu 2.2; O 0.2; Zr 0.1 Aerospace
7178 88.1 Zn 6.8; Mg 2.7; Cu 2.0; Cr 0.26 Universal, aerospace
7255 87.5 Zn 8.0; Mg 2.1; Cu 2.3; Zr 0.1 Plate, aerospace[8]
7475 90.3 Zn 5.7; Mg 2.3; Si 1.5; Cr 0.22 Universal, aerospace

References
  1. Placzankis, Brian E. (September 2009). General Corrosion Resistance Comparisons of Medium- and High-Strength Aluminum Alloys for DOD Systems Using Laboratory-Based Accelerated Corrosion Methods (Report). U.S. Army Research Laboratory. DTIC ADA516812; ARL-TR-4937. Retrieved 11 August 2018 – via Internet Archive.
  2. Sahamit machinery 7022
  3. RSP alloys datasheet
  4. "7055 Alloy -T7751 Plate and -T77511 EXTRUSIONS" (PDF). Archived from the original (PDF) on 2017-12-22. Retrieved 2023-02-25.
  5. "Aluminum alloy 7065" (PDF). Archived from the original (PDF) on 2017-12-22. Retrieved 2023-02-25.
  6. "Aluminum alloy 7085 High strength, high toughness, corrosion-resistant thick plate" (PDF). Archived from the original (PDF) on 2017-12-22. Retrieved 2023-02-25.
  7. Davis, Joseph R; Handbook Committee, ASM International (1 May 2000). "Cobalt". Nickel, cobalt, and their alloys. p. 354. ISBN 978-0-87170-685-0.
  8. "Aluminum alloy 7255-T7751 Very high strength, fatigue-resistant plate" (PDF). Archived from the original (PDF) on 2017-12-22. Retrieved 2023-02-25.

Further reading
  • Publication series of the DKI, Berlin, number L5 "Copper-Zinc alloys".
  • Foundry lexicon. 17. Edition, Schiele and Schön, Berlin, ISBN 3-7949-0606-3
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