Institute I: General Materials Properties
Dept. Materials Science  —   Faculty of Engineering  —  Friedrich-Alexander-University  —  UnivIS  —  Wiki
Prof. Motomichi Koyama will be visiting WW1
Prof. Motomichi Koyama from Tohoku University, Japan will be visiting WW1 on Feb. 19, 2020. He will give a talk on Wednesday, Feb 19 at 14:00 in Room 3.31, Martensstraße 5. He will talk about "Effects of dislocation planarity and compositional complexity on hydrogen embrittlement of austenitic steels".
Stable austenitic steels have been recognized as hydrogen-resistant materials. However they also show hydrogen-assisted failure when exposed to a severe hydrogen atmosphere, e.g. 100-MPa hydrogen gas. In this talk, we present two examples of hydrogen embrittlement of stable austenitic steels: Fe25Cr1N steel and equiatomic high-entropy alloy. The former shows extremely enhanced dislocation planarity because of the Cr-N coupling. The strong dislocation planar motion causes stress concentration on grain boundaries, which results in intergranular fracture when hydrogen is introduced. In addition, the dislocation planar array can act as quasi-cleavage fracture path. Therefore, the hydrogen-assisted failure in the high-nitrogen steel occurs via dislocation-planarity-driven microstructural cracking. The high-entropy alloy shows hydrogen-assisted intergranular fracture. The brittleness can be reduced by grain refinement or reducing Mn content. In the presentation, details of these phenomena are given with electron channeling contrast images.