Effect of Strain Rate on Stress Corrosion Cracking of Austenitic Stainless Steel in MgCl₂ Solutions

The effect of strain rate on the stress corrosion cracking (SCC) of an austenitic stainless steel in MgCl₂ solutions has been investigated by using a constant strain rate method over the range of strain rates from 4x10⁻³ mm/min to 6 mm/min. Crack propagation mode (intergranular vs transgranular) was a function of strain rate and temperature. At low strain rates, the rate determining step of the SCC corresponded to the formation of slip steps, but at higher strain rates, the rate determining step appeared to be a corrosion process on the slip steps. SCC was most prevalent when the formation rate of the slip steps was equal to the corrosion rate of the steps. The mechanism of SCC in this system has been discussed by considering both the formation rate of slip steps and the corrosion rate of these steps.