日本金属学会誌

J. Japan Inst. Metals, Vol. 40, No. 6 (1976),
pp. 618-624

Stress Corrosion Cracking of Al-4.57%Zn-1.35%Mg Alloy

Hideo Hirano1, Michinori Takano2 and Saburo Shimodaira3

1Graduate School, Tohoku University, Sendai. Present address: Central Research Institute of Electric Power Industry, Tokyo
2The Research Institute for Iron, Steel and Other Metals, Tohoku University, Sendai
3The Research Institute for Iron, Steel and Other Metals, Tohoku University, Sendai. Present address: Research Institute of Metals, Showa Denko Co., Ltd., Tokyo

Abstract:

The mechanism of a stress-corrosion cracking of Al-4.57%Zn-1.35%Mg and Al-4.43%Zn-1.34%Mg-0.13%Cu alloys in 3%NaCl aqueous solution was investigated electrochemically and metallurgically.
A constant load test and a constant strain rate test were carried out to determine the effect of aging treatments on a susceptibility to stress-corrosion cracking. The results obtained from these tests showed that both alloys aged at 120°C for 24 hr became most susceptible to stress-corrosion cracking, which was accelerated by an anodic polarization or a cathodic polarization of -1000 mV (SCE). In the former polarization, stress-corrosion cracking occurred by a stress-assisted intergranular corrosion, and in the later condition it took place by a co-operative actions of pitting which produced by a selective dissolution of high density η'-particles along grain boundaries and the stress concentration wherein. Under the cathodic polarization from -1200 mV to -1800 mV (SCE), the specimens suffered general corrosion, and stress-corrosion cracking did not occur. Both anodic and cathodic polarization curves showed a good relation to aging treatments but no relation to stress-corrosion cracking.


(Received 1975/11/12)

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