Hydrogen - dislocation interactions in a low-copper 7xxx aluminium alloy: About the analysis of interrupted stress corrosion cracking tests

Abstract

Aluminium alloys are susceptible to stress corrosion cracking (SCC) in specific conditions, which can be associated with hydrogen embrittlement (HE).Interrupted SCC tests are often performed to evaluate the susceptibility of the samples to a specific environment under mechanical loading. Those tests consist in a pre-corrosion step, which can lead to hydrogen-precharging, followed by a tensile test in air. The present study, performed on a 7046 aluminium alloy, confirmed literature data showing that tensile tests in laboratory air on as-polished samples at sufficiently low strain rates led to a significant hydrogen ingress. Depending on the sample microstructure, various hydrogen - dislocations and dislocations - microstructure interactions could be effective leading to a change in the tensile behaviour of the samples. Such a phenomenon could lead to misinterpret the interrupted SCC tests performed on hydrogen-precharged samples. In the present study, a corrected SCC susceptibility factor was defined to better analyse the interrupted SCC tests.