Interplay between hydrogen, precipitates and dislocation substructures in pipeline steel

Hydrogen embrittlement refers to the scenario where dissolved hydrogen reduces the strength and ductility of a material, which can cause premature and abrupt failure to pipelines that transport hydrogen gas.

To address this issue, a comprehensive understanding of the interplay between hydrogen, precipitates and dislocation substructures is required.

However, direct in-situ observation of the kinetics of dislocation substructures in a bulk material is still not possible.This project will run for 4-years, I will work together with a PhD student, to depict a time-resolved, comprehensive picture of hydrogen and precipitate-facilitated evolution of dislocation substructures, and further elucidate the connection of the substructures to hydrogen induced fracture.

To achieve this, advanced post-mortem experimental characterisation techniques will be employed to observe the dislocation substructures and to measure the associated local stain partitioning.

Then, a multiscale numerical model will be developed to capture the dislocation kinetics that lead to the formation of the substructures.

The model will reproduce the early-stage formation of dislocation entanglements around single hydrogen-trapping precipitates, as well as dislocation patterning that arises at a global level.

Finally, hydrogen induced fracture will be quantitatively assessed.These outcomes will provide a robust and reliable basis for designing and testing pipeline steels that are resistant to hydrogen embrittlement.