Hydrogen trapping and embrittlement in high-strength Al alloys
Huan Zhao, Poulami Chakraborty, Dirk Ponge, Tilmann Hickel, Binhan Sun, Chun‐Hung Wu, Baptiste Gault, Dierk Raabe
Abstract
Abstract Ever more stringent regulations on greenhouse gas emissions from transportation motivate efforts to revisit materials used for vehicles 1 . High-strength aluminium alloys often used in aircrafts could help reduce the weight of automobiles, but are susceptible to environmental degradation 2,3 . Hydrogen ‘embrittlement’ is often indicated as the main culprit 4 ; however, the exact mechanisms underpinning failure are not precisely known: atomic-scale analysis of H inside an alloy remains a challenge, and this prevents deploying alloy design strategies to enhance the durability of the materials. Here we performed near-atomic-scale analysis of H trapped in second-phase particles and at grain boundaries in a high-strength 7xxx Al alloy. We used these observations to guide atomistic ab initio calculations, which show that the co-segregation of alloying elements and H favours grain boundary decohesion, and the strong partitioning of H into the second-phase particles removes solute H from the matrix, hence preventing H embrittlement. Our insights further advance the mechanistic understanding of H-assisted embrittlement in Al alloys, emphasizing the role of H traps in minimizing cracking and guiding new alloy design.