[Paper Review] Influence of Hydrogen on Dislocation Relaxation in BCC Iron: Atomistic Mechanisms and Implications

Sanjay Manda, Madhur Gupta+5 more|arXiv (Cornell University)|Feb 26, 2026

Microstructure and mechanical properties0 citations

TL;DR

The paper uses a multiscale MD–KMC framework to study how hydrogen affects dislocation relaxation in BCC iron, showing hydrogen lowers kink nucleation barriers but raises migration barriers, captures Snoek–Koster peaks, and reveals a linear link between hydrogen content and internal friction loss.

ABSTRACT

In this study, the influence of pure dislocation and hydrogen-dislocation interactions on anelastic response or internal friction relaxation peaks in bcc-iron was investigated. These relaxations are primarily governed by thermally activated kink nucleation and kink migration events. An atomistic multiscale framework, coupling molecular dynamics (MD) and kinetic Monte Carlo (KMC) simulations, was developed to investigate the underlying atomistic mechanisms behind dislocation-relaxation peaks. MD simulations revealed that the presence of hydrogen atoms near the dislocation core facilitates the kink nucleation process by reducing the nucleation barrier while enhancing the barrier for dislocation migration. The KMC model captured Snoek-Koster peaks arising from the Cottrell atmosphere formed by hydrogen atoms and clusters around the dislocation core, providing insights into the atomistic mechanisms controlling these relaxations. Furthermore, the proposed computational scheme elucidated a unique linear relationship between hydrogen content and the internal friction loss factor, offering a methodology for hydrogen detection and quantification.

Motivation & Objective

• Investigate how pure dislocation and hydrogen–dislocation interactions influence anelastic relaxation (internal friction) in BCC iron.
• Elucidate atomistic mechanisms behind dislocation relaxation via kink nucleation and migration in the presence of hydrogen.
• Develop a multiscale modeling framework combining MD and kinetic Monte Carlo to connect atomic processes with macroscopic relaxation.
• Identify signatures of hydrogen around dislocations (Cottrell atmosphere) and their impact on relaxation peaks.

Proposed method

• Develop an atomistic multiscale framework coupling molecular dynamics (MD) and kinetic Monte Carlo (KMC) simulations.
• Use MD to characterize how hydrogen near a dislocation core affects kink nucleation and dislocation migration barriers.
• Construct a KMC model to capture relaxation peaks (Snoek–Koster) due to hydrogen atmospheres and Cottrell clusters.
• Analyze the relationship between hydrogen content and the internal friction loss factor.
• Provide a methodology that links atomistic hydrogen content to measurable anelastic response.

Experimental results

Research questions

• RQ1 How does hydrogen presence near a dislocation core influence the barrier for kink nucleation in BCC iron?
• RQ2 How does hydrogen affect the barrier for dislocation migration and overall dislocation mobility?
• RQ3 What is the role of hydrogen-induced atmospheres and Cottrell clusters in producing Snoek–Koster relaxation peaks?
• RQ4 Can hydrogen content be linearly related to the internal friction loss factor, enabling hydrogen detection/quantification?

Key findings

• Hydrogen near the dislocation core lowers the nucleation barrier for kink nucleation.
• Hydrogen increases the barrier for dislocation migration, hindering mobility.
• The KMC model captures Snoek–Koster peaks arising from hydrogen atmospheres and Cottrell clusters around the dislocation core.
• The computational scheme reveals a linear relationship between hydrogen content and the internal friction loss factor.
• The study provides atomistic insights into how hydrogen modulates anelastic response in BCC iron.