The effects of different Zn/Mg ratios on the microstructure, mechanical properties and resistance of stress corrosion cracking of peak-aged 7005 aluminum alloy were investigated. It was found that the Zn/Mg ratio played a very important role in controlling the aging time, the electrical conductivity of the hardness peak point and the resistance of stress corrosion cracking of the alloy. With the increase of Zn/Mg ratio (wt. %), the time taken by the alloy to achieve the peak hardness value gradually increases aging at 120 °C. When the Zn/Mg ratio is in the range from 2.27% to 2.62%, the precipitate phase of the alloy after peak-aged is mainly dominated by smaller disc-like η’ phase and GP I (Guinier Preston) zones, the grain boundary precipitates are slender and continuous and the PFZ (precipitate free zones) is narrow. However when this value is in the range from 3.01% to 4.08%, precipitation phase in matrix of the alloy is mainly composed of short-rod η′ phase and GP II zones, the precipitation phases within the grain boundary are large and distribute intermittently and the PFZ is narrower. The results of SSRT (slow strain rate tests) show that when Zn/Mg ≥ 3.61, the 7005 aluminum alloy at peak-aged has good resistance of stress corrosion cracking in 3.5% NaCl + 0.5% H2O2 aqueous solution. However, when Zn/Mg ≤ 3.01, the strength of the alloy sharply decreases in 3.5% (wt. %) NaCl + 0.5% (wt. %) H2O2 aqueous solution.

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is currently pursuing a B.S. degree in Computer Science Statistics. Her research interests include natural language processing, data mining, and optimization algorithms.

The precipitation of 7N01 alloy after three-step ageing treatment at 65°C, 100°C and 150°C has been investigated. The SAED results show that at 65°Cpre-aging the GPI zones were precipitated from the quenched solid solution and aging at 150°C results in evolution of the GPI zones formed during under ageing into the η’ phase. It was found that compared with the two-stage aging(T74) and T6 aging, pre-aging at 65°C significantly increased number density of η’ phase. The modified microstructure results in tensile properties comparable to that of the T6 temper, but with significantly improved the resistance of stress corrosion cracking performance.