Environmental TEM of Hydrogen–Dislocation and Interface Interactions in Metals by Professor Degang Xie

NTU MSE Seminar Hosted by Nanyang Assistant Professor Eason Y.-S. Chen

Abstract

Hydrogen can profoundly alter plasticity and interfacial stability in metals, yet direct experimental access to the underlying mechanisms remains limited. Here, we use in situ environmental transmission electron microscopy (ETEM), combined with quantitative nanomechanical testing, to investigate hydrogen effects on dislocation motion and interfacial damage in Al and Fe. The experiments directly reveal hydrogen-mediated changes in dislocation mobility and pinning, while separating intrinsic hydrogen effects from surface and oxide-related constraints. ETEM observations further show hydrogen accumulation and blister formation at metal/oxide interfaces, leading to cavity growth and eventual oxide spallation. The cavity evolution depends strongly on crystallographic orientation and temperature, with a transition near 150 °C from cavity growth to shrinkage. These observations provide direct mechanistic insight into hydrogen–defect interactions and illustrate how environmental TEM can bridge atomic-scale processes with hydrogen-induced degradation in structural metals.

Biography

Professor Degang Xie
Xi’an Jiaotong University

Degang Xie is a Professor of Materials Science and Engineering at Xi’an Jiaotong University and Deputy Director of the XJTU–Hitachi Research and Development Center. His research focuses on hydrogen–defect interactions and hydrogen embrittlement in metals, micro- and nanoscale mechanical behavior, in situ environmental electron microscopy, and corrosion of metallic materials. He has developed experimental approaches that combine environmental TEM/SEM with quantitative micro- and nanomechanical testing to directly probe hydrogen effects on dislocations, interfaces, and deformation processes. His work has been published in journals including Nature Materials and Nature Communications. He was an Alexander von Humboldt Fellow and has received the IFSM Young Scientist Award. His current research also extends to high-purity magnesium and biodegradable metallic materials.