In this paper, the influence of T6, T74 and RRA aging treatments on microstructure, strength and corrosion behaviour of high Zn content Al–Zn–Mg–Cu alloy was investigated by tensile properties tests, inter-granular corrosion (IGC) tests, exfoliation corrosion (EXCO) tests, polarisation tests, metallographic microscope and transmission electron microscopy (TEM) analysis. The results show that the T74 and RRA temper can increase the size and the distribution discontinuity of the grain boundaries precipitates (GBPs), thus leading to improvement of the corrosion resistance. However, with the coarser matrix precipitates (MPs) relative to T6 treatment, RRA and T74 temper both have a decrease in strength. Besides, all the performances (including mechanical properties and corrosion properties) of the RRA treatment show an intermediate level relative to T6 and T74. Therefore, we can select the appropriate heat treatment process according to the different performance requirements in the industrial production.
HeinzAHaszlerAKeidelCMoldenhauerSBenedictusR and MillerWS: ‘Recent development in aluminum alloys for aerospace applications’Mater. Sci. Eng. A2000A280102–107.
2.
RendigsKH: ‘Aluminum structures used in aerospace-status and prospects’Mater. Sci. Forum199624211–24.
3.
SrivatsanTSAnandSSriramS and VasudevanVK: ‘The high-cycle fatigue and fracture behavior of aluminum alloy 7055’Mater. Sci. Eng. A2000A281292–304.
4.
WilliamsJC and StarkeEAJR: ‘Progress in structural materials for aerospace systems’Acta Mater.2003515775–5799.
5.
WuLMWangWHHsuYF and ShanT: ‘Effects of homogenization treatment on recrystallization behavior and dispersoid distribution in an Al–Zn–Mg–Sc–Zr alloy’J. Alloy Compd2008456163–169.
6.
NajjarDMagninT and WarnerTJ: ‘Influence of critical surface defects and localized competition between anodic dissolution and hydrogen effects during stress corrosion cracking of a 7050 aluminium alloy’Mater. Sci. Eng. A1997A238293–302.
7.
URALK: ‘A study of optimization of heat-treatment conditions in retrogression and reaging treatment of 7075-T6 aluminum alloy’J. Mater. Sci. Lett.199413383–385.
8.
NingALLiuZYPengBS and ZengSM: ‘Redistribution and re-precipitation of solute atom during retrogression and reaging of Al-Zn-Mg-Cu alloys’Trans. Nonferrous Met. Soc. China2007171005–1011.
9.
ZhouHRLiXGXiaoK and DongCF: ‘The corrosion behavior of aluminum alloy 7A04 under cyclic wet-dry immersion conditions’Rare Met. Mater. Eng.200938293–298.
10.
ZhangWL and FrankelGS: ‘Transitions between pitting and intergranular corrosion in AA2024’Electrochim. Acta2003481193–1210.
11.
AndreattaFTerrynH and de WitJHW: ‘Corrosion behaviour of different tempers of AA7075 aluminium alloy’Electrochim. Acta2004492851–2862.
12.
ConnollyBJDeffenbaughKLMoranAL and MichelleGK: ‘Environmentally assisted crack growth rates of high-strength aluminum alloys’JOM20035549–52.
13.
FanXGJiangDMZhongLWangT and RenSY: ‘Influence of microstructure on the crack propagation and corrosion resistance of Al–Zn–Mg–Cu alloy 7150’Mater. Charact.200758(1)24–28.
14.
RamgopalTGoumaPI and FrankelGS: ‘Role of grain-boundary precipitates and solute-depleted zone on the intergranular corrosion of aluminum alloy 7150’Corrosion200258687–697.
15.
MarlaudTMalkiBHenonCDeschampsA and BarouxB: ‘Relationship between alloy composition, microstructure and exfoliation corrosion in Al–Zn–Mg–Cu alloys’Corros. Sci.2011533139–3149.
16.
LiJFPengZWLiCXJiaZQChenWJ and ZhengZQ: ‘Mechanical properties, corrosion behaviors and microstructures of 7075 aluminium alloy with various aging treatments’Trans. Nonferrous Met. Soc. China200818755–762.
17.
PARKJK: ‘Influence of retrogression and re-ageing on the strength and stress corrosion resistance of aluminum alloy 7075-T6’Mater. Sci. Eng. A1988A103223–231.
18.
LiJFBirbilisNLiCXJiaZQCaiB and ZhengZQ: ‘Influence of retrogression temperature and time on the mechanical properties and exfoliation corrosion behavior of aluminium alloy AA7150’Mater. Charact.2009601334–1341.
19.
‘Tension test method at room-temperature’National standard of China, GB/T 228-2002.
20.
‘Metallic materials – determination of plane-strain fracture toughness’National standard of China, GB/T 4161-2007.
21.
‘Test method for intergranular corrosion of aluminium alloy’National standard of China, GB7998-2005.
22.
‘Test method of exfoliation corrosion for wrought aluminium and aluminium alloys’National standard of China, GB/T22639-2008.
23.
LacomWDegischerHPZahraA and ZahraCY: ‘Decomposition processes in an Al-5% Zn-1% Mg alloy. Pt. 3. Reversion of G-P zones’Z. Metallkd198273781–785.
24.
ShaG and CerezoA: ‘Early-stage precipitation in Al–Zn–Mg–Cu alloy (7050)’Acta Mater.2004524503–4516.
25.
ShaG and CerezoA: ‘Kinetic Monte Carlo simulation of clustering in an Al–Zn–Mg–Cu alloy (7050)’Acta Mater.200553907–917.
26.
BuhaJLumleyRN and CroskyAG: ‘Secondary ageing in an aluminium alloy 7050’Mater. Sci. Eng. A2008A492(1)1–10.
27.
MarlaudTDeschampsABleyFLefebvreW and BarouxB: ‘Influence of alloy composition and heat treatment on precipitate composition in Al–Zn–Mg–Cu alloys’Acta Mater.201058248–260.
28.
MarlaudTDeschampsABleyFLefebvreW and BarouxB: ‘Evolution of precipitate microstructures during the retrogression and re-ageing heat treatment of an Al–Zn–Mg–Cu alloy’Acta Mater.2010584814–4826.
29.
DavisJ R (ed.): ‘Corrosion of aluminum and aluminum alloys’28–29; 1999Materials Park, OHAmerica Society for Metals.
30.
HuangLPChenKHLiS and SongM: ‘Influence of high-temperature pre-precipitation on local corrosion behaviors of Al–Zn–Mg alloy’Scr. Mater.200756305–308.
31.
KnightSPBirbilisNMuddleBCTruemanAR and LynchSP: ‘Correlations between intergranular stress corrosion cracking, grain-boundary microchemistry, and grain-boundary electrochemistry for Al–Zn–Mg–Cu alloys’Corros. Sci.2010524073–4080.
32.
HanNMZhangXMLiuSDHeDG and ZhangR: ‘Effect of solution treatment on the strength and fracture toughness of aluminum alloy 7050’J. Alloy Compd20115094138–4145.
33.
WlokaJHackT and VirtanenS: ‘Influence of temper and surface condition on the exfoliation behaviour of high strength Al–Zn–Mg–Cu alloys’Corros. Sci.2007491437–1449.
34.
RobinsonMJ: ‘Mathematical modeling of exfoliation corrosion in high strength aluminum alloys’Corros. Sci.198222775–790.
35.
RobinsonMJ: ‘The role of wedging stresses in the exfoliation corrosion of high strength aluminum alloys’Corros. Sci.198323887–899.
36.
LiJFZhengZQLiSCChenWJRenWD and ZhaoXS: ‘Simulation study on function mechanism of some precipitates in localized corrosion of Al alloys’Corros. Sci.2007492436–2449.
37.
XiaoYPPanQLLiWBLiuXY and HeYB: ‘Influence of retrogression and re-aging treatment on corrosion behaviour of an Al–Zn–Mg–Cu alloy’Mater. Des.2011322149–2156.
38.
VianaFPintoAMPSantosHMC and LopesAB: ‘Retrogression, re-aging of 7075 aluminum alloy: microstructural characterization’J. Mater. Process. Technol.199992/9354–59.
39.
HollingsworthEH and HunsickerHY: ‘Corrosion of aluminum and aluminum alloy’in ‘Metals handbook’, 9th edn583–609; 1987Materials Park, OHASM International.
