The role of hydrogen in the corrosion-induced reduction of K_R critical fracture toughness and intergranular secondary cracking in a high-strength aluminium alloy

University of Pretoria, Department of Materials Science and Metallurgical Engineering, Lynnwood Road, Hatfield, Pretoria 0002, South Africa

Abstract

It is shown that short-term exposure of AA2024-T3 material to an exfoliation corrosion (EXCO) solution leads to a reduction of non-plane strain fracture toughness and the formation of secondary surface cracks during plastic straining. The study aims to establish whether the secondary cracking effect and the fracture toughness reduction are due to corrosion-induced hydrogen embrittlement. It is hypothesized that, if hydrogen-embrittlement is the cause of the intergranular secondary cracking (ISC) and fracture toughness degradation, post-exposure heat treatment would restore the mechanical property degradation and reduce the ISC formation through the desorption of diffusible hydrogen. It was found that the solution and ageing heat treatments restored the fracture toughness of the alloy. However, the ISC behaviour persisted. The results are discussed and interpreted in terms of hydrogen embrittlement theory.