Findings could guide design of new embrittlement-resistant materials.
Researchers at McGill University announced that they may have found a clue to explaining a corrosive process called hydrogen embrittlement. Since its discovery, hydrogen embrittlement has been a problem for the design of materials in various industries, from battleships to aircraft and nuclear reactors. The problem stems from the fact that hydrogen can dissolve and migrate within metals making them brittle and prone to failure.
Jun Song, an Assistant Professor in Materials Engineering at McGill University, and Prof. William Curtin, Director of the Institute of Mechanical Engineering at École polytechnique fédérale de Lausanne in Switzerland, say the problem may be rooted in how hydrogen modifies material behaviours at the nanoscale. Under normal conditions, metals can undergo plastic deformation when subjected to forces. This plasticity stems from the ability of nano- and micro-sized cracks to generate “dislocations” within the metal.
“Dislocations can be viewed as vehicles to carry plastic deformation, while the nano- and micro-sized cracks can be viewed as hubs to dispatch those vehicles,” Song explains. “The desirable properties of metals, such as ductility and toughness, rely on the hubs functioning well. Unfortunately those hubs also attract hydrogen atoms. The way hydrogen atoms embrittle metals is by causing a kind of traffic jam: they crowd around the hub and block all possible routes for vehicle dispatch. This eventually leads to the material breaking down.”
As part of their study, published in Nature Materials, Song and Curtin performed computer simulations to reveal how hydrogen atoms move within metals and how they interact with metal atoms. This simulation was followed by kinetic analysis, to link the nanoscale details with macroscopic experimental conditions. This model was found to accurately predict embrittlement in a variety of iron-based steels and may provide a basis for designing embrittlement-resistant materials.
The research was funded in part by the Natural Sciences and Engineering Research Council of Canada, the U.S. Office of Naval Research and by the General Motors/Brown Collaborative Research Lab on Computational Materials.