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Published October 2022 | Supplemental Material + In Press
Journal Article Open

Hydrogen-enhanced grain boundary vacancy stockpiling causes transgranular to intergranular fracture transition

Abstract

The attention to hydrogen embrittlement (HE) has been intensified recently in the light of hydrogen as a carbon-free energy carrier. Despite worldwide research, the multifaceted HE mechanism remains a matter of debate. Here we report an atomistic study of the coupled effect of hydrogen and deformation temperature on the pathway to intergranular fracture of nickel. Uniaxial straining is applied to nickel Σ5(210)[001] and Σ9(1-10)[22-1] grain boundaries with or without pre-charged hydrogen at various temperatures. Without hydrogen, vacancy generation at grain boundary is limited and transgranular fracture mode dominates. When charged, hydrogen as a booster can enhance strain-induced vacancy generation by up to ten times. This leads to the superabundant vacancy stockpiling at the grain boundary, which agglomerates and nucleates intergranular nanovoids eventually causing intergranular fracture. While hydrogen tends to persistently enhance vacancy concentration, temperature plays an intriguing dual role as either an enhancer or an inhibitor for vacancy stockpiling. These results show good agreement with recent positron annihilation spectroscopy experiments. An S-shaped quantitative correlation between the proportion of intergranular fracture and vacancy concentration was for the first time derived, highlighting the existence of a critical vacancy concentration, beyond which fracture mode will be completely intergranular.

Additional Information

© 2022 The Author(s). Published by Elsevier Ltd on behalf of Acta Materialia Inc. Under a Creative Commons license - Attribution 4.0 International (CC BY 4.0). Received 24 April 2022, Revised 8 August 2022, Accepted 15 August 2022, Available online 17 August 2022. Y.D. acknowledge the financial support provided by the Research Council of Norway under the M-HEAT project (Grant No. 294689) and the HyLINE project (Grant No. 294739). All simulations are carried out on the Fram (Grant No. NN9110K, NN9391K) high-performance computer clusters at NTNU, Trondheim. Author contribution. The project was planned and supervised by Z.Z., J.H., H.Y. The simulation design and data analysis were performed by Y.D. All authors participated in the discussion and co-wrote the paper. Data availability. The data that support the findings of this study are available from the corresponding authors upon request. The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

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Supplemental Material - ScienceDirect_files_18Aug2022_00-09-15.537.zip

In Press - 1-s2.0-S1359645422006590-main.pdf

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Additional details

Created:
August 22, 2023
Modified:
October 24, 2023