Hydrogen embrittlement (HE) of commercial alloys has been widely studied for over a hundred years, whereas it has been rarely attempted to design new alloys targeting superior HE-resistance. This is largely due to two reasons: (i) It is experimentally challenging to screen the enormous compositional space in a feasible manner, since it would require monitoring of H-diffusivity, trapping, strength, fracture toughness, defect behavior – all laborious to investigate due to spatial and temporal scales involved with HE. (ii) Since HE mechanisms are not fully understood, it is difficult to develop HE-resistant alloy design concepts, without any experimental “trial-error”.
This project, proposed by a multi-institutional team led by MIT, aims to develop a novel high-throughput approach for discovering HE-resistant alloys, which is based on combinatorial compositional screening of metastability effects by in situ scanning electron microscopy H-analyses. Hundreds of individual alloy samples in a few-micron scale with compositional variation (“Composition spread islands”) will be fabricated on a single substrate using a combinatorial co-sputtering technique. The team will develop an integrated characterization system based on a scanning electron microscope to characterize microstructures and properties of alloy islands under H-attack. Using this novel characterization approach, alloy compositions with superior HE-resistance will be identified in a high-throughput way. HE-resistance of the discovered alloy compositions will also be verified by utilizing a range of multi-scale tools: from accelerated simulations in atomic scale to in-service-condition mechanical tests in bulk scale.
This research will lead to new alloys and surface structures with high resistance against HE, which are relevant for hydrogen refueling applications. Improvement of strength, fracture toughness and HE-resistance will reduce the required amount of materials and extend service life of metal components under H-environment, and eventually reduce cost per time compared to the current state-of-art using low alloy steels and austenitic stainless steels. This work is sponsored by Office of Energy Efficiency & Renewable Energy, Department of Energy, and the team collaborates with the H-Mat consortium.