Reviewed by Lexie CornerJul 22 2024
An international group of researchers from Texas A&M University and Lee University studied the development of cracks in samples of Inconel 725, a nickel-base alloy recognized for its strength and resistance to corrosion, that were initially perfect and free of fractures. The journal Science Advances published this study.
Metals are frequently chosen for infrastructure projects due to their endurance when choosing materials. However, metals can become brittle and fail if placed in a hydrogen-rich environment, like water. This phenomenon, known as hydrogen embrittlement, has confused researchers since the middle of the 19th century.
Currently, several working theories try to explain hydrogen embrittlement. The study's findings disprove one of the more widely accepted theories, hydrogen-enhanced localized plasticity (HELP), in the instance of this alloy.
Plasticity, often known as irreversible deformation, is concentrated in certain spots inside a material rather than occurring uniformly throughout. According to HELP, cracks start in places with the maximum localized plasticity.
As far as I know, ours is the first study that actually looks in real time to see where cracks initiate and is not at locations of highest localized plasticity. Our study tracks both the localized plasticity and the crack initiation locations in real time.
Dr. Michael J. Demkowicz, Professor and Study Co-Author, Department of Materials Science and Engineering, Texas A&M University
Demkowicz is also Liu’s Ph.D. advisor.
It is critical to monitor the onset of cracks in real time. When a sample is examined after a crack has formed, the hydrogen has already leaked out of the material, making it impossible to determine the mechanism causing the damage.
Hydrogen easily escapes from metals, so you cannot figure out what it does to embrittle a metal by examining specimens after they have been tested. You have to look while you are testing.
Dr. Michael J. Demkowicz, Professor and Study Co-Author, Department of Materials Science and Engineering, Texas A&M University
This work lays the foundation for more accurate hydrogen embrittlement predictions. Hydrogen has the potential to displace fossil fuels as a clean energy source in the future. If this transformation were to occur, all of the infrastructure currently in place for the storage and use of fossil fuels would be vulnerable to hydrogen embrittlement. To prevent unanticipated failures and enable a future hydrogen economy, embrittlement prediction is essential.
Liu provided additional data analysis and manuscript preparation at Washington and Lee, while the experiments and initial data analysis for this study were carried out at Texas A&M. Liu, Demkowicz, and Lai Jiang, a doctorate candidate at Texas A&M, are Co-authors of this work.
Journal Reference:
Liu, M., et al. (2024) Role of slip in hydrogen-assisted crack initiation in Ni-based alloy 725. Science Advances. doi.org/10.1126/sciadv.ado2118.