Effects of controlled potential on fracture time,
tf, crack-initiation time,
ti and crack-propagation time,
tc in the stress corrosion cracking (SCC) of an Al-6.13 wt%Zn-2.10wt%Mg alloy were investigated by the Weibull's distribution method. Specimens were solutlon treated at 460°C for 1h, quenched into ice-water and aged at 120°C for 24h. The SCC test was performed at 33°C in 3.3%NaCl+0.2%H
2O
2 aqueous solution of pH 5.2 under controlled potential. The constant stress of 60% of the yield stress was applied. All the shape parameters (
m) were larger than 1 indicating the wearing-out failure. The shape parameters for
tf and
ti decreased under the nobler potential than the rest one, while the shape parameters for
tf, ti and
tc increased under the lower potential than the rest. The life time, η for
tf and
ti decreased under the nobler potential than the rest and increased under the lower potential than the rest. The life time for
tc was shorter than the half for
ti. The major part of the life time for
tf was that for
ti. This implies that the life time for
tf depends on that for
ti. The probability density function
f(t) which corresponded to the actual failure was determined from the values of
m and μ.
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