AlMgZnCu hydrogen embrittlement by nanograin boundary decomposition

Understanding the Hydrogen embrittlement (HE) mechanism on the miscroscopic level has been a long-standing challenge. In this work, a systematic computational work based on the first-principles simulations and Ref as well as the ab initio molecular dynamics unveiled the effects of 19 metallic solutes on the HE of AlMgZnCu alloys with Σ3(111), Σ5(210), Σ5(310), Σ7(123), and Σ9(221) grain boundaries (GBs). The effects of the atomic size of these solutes on the complex segregation energy (SE) and GB energy were investigated, and the effect of temperature on the H concentration of the AlMgZnCu alloys was analyzed using a Gaussian distribution of complex SE. It is determined that the HE process involves the following sequence of phenomena: fracture surface formation → crack propagation → GB fracturing. The key findings of this work are summarized as follows: (i) the SE and GB/free surface energy depends linearly on the atomic sizes of the alloy; (ii) the crack could be healed at a critical temperature of 673 K; (iii) A gene diagram has been developed to show the temperature dependence of the segregation and cohesion of H concentration.