Effects of applied stress σ(kg/mm
2) and test temperature T (°K) on stress corrosion life time (min) in ST-direction of Al-Zn-Mg alloy thick plate were investigated in a mixed chromic acid solution.
T being constant, linear relation existed between logσ and logt, and σ being constant, linear relation existed also between logt and 1/T. Effects of σ and T on t were srepresented by the equation, 1/t = K σ
-1/n exp (-ΔH/RT) Herein, K, n, ΔH and R are constants, and R is gas constant 1.98 cal mol
-1 deg
-1, K is 5.5×10
3, n is 0.508 and ΔH is activation constant 12, 800 cal mol
-1. It is considered to be more reasonable that applied stress σ should be replaced by σ
N, perpendicular component of applied stress to grain boundary.
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