A mesoscale phase-field model of intergranular liquid lithium corrosion of ferritic/martensitic steels

2025-06-03

AI Summary

This study addresses the challenge of predicting intergranular corrosion of ferritic/martensitic steels in liquid lithium. We develop the first mesoscale phase-field model that eliminates the need for explicit interface tracking or specialized boundary treatments. The model formulates solid/liquid mass transport driven by chromium concentration gradients, inherently capturing preferential grain-boundary corrosion. It uniquely couples anisotropic grain-boundary diffusion with arbitrary 2D/3D polycrystalline microstructures. Through parametric sensitivity analysis, we quantitatively identify near-surface grain density as the dominant factor controlling corrosion kinetics, followed by grain size and chromium depletion layer thickness. The model successfully reproduces experimentally measured weight loss and corrosion depth profiles. This work establishes a new paradigm for mechanistic investigation and lifetime prediction of advanced structural materials exposed to liquid metal environments.

Technology Category

• Machine Learning: Large Multimodal Models (LMMs)
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Abstract

A phase-field model is developed to simulate intergranular corrosion of ferritic/martensitic steels exposed to liquid lithium. The chromium concentration of the material is used to track the mass transport within the metal and liquid (corrosive) phase. The framework naturally captures intergranular corrosion by enhancing the diffusion of chromium along grain boundaries relative to the grain bulk with no special treatment for the corrosion front evolution. The formulation applies to arbitrary 2D and 3D polycrystalline geometries. The framework reproduces experimental measurements of weight loss and corrosion depth for a 9 wt% Cr ferritic/martensitic steel exposed to static lithium at 600 $^circ$C. A sensitivity analysis, varying near-surface grain density, grain size, and chromium depletion thickness, highlights the microstructural influence in the corrosion process. Moreover, the significance of saturation is considered and evaluated. Simulation results show that near-surface grain density is a deciding factor, whereas grain size dictates the susceptibility to intergranular corrosion.

Problem

• Modeling intergranular corrosion in steels exposed to liquid lithium
• Tracking chromium transport to simulate corrosion dynamics
• Analyzing microstructural impacts on corrosion susceptibility

Innovation

• Phase-field model simulates intergranular corrosion
• Chromium concentration tracks mass transport
• Captures corrosion via enhanced grain boundary diffusion