Multiphysics Modeling of Environment-assisted Cracking Properties of Advanced Materials for Aerospace and Marine Application

Abstract

This dissertation develops a Multiphysics phase field-based model to predict the initiation, propagation, and recovery of corrosion damage in metallic alloys by coupling electrochemical dissolution, mechanical deformation, and repassivation within a thermodynamically consistent formulation. The framework addresses the challenge of predicting stress corrosion cracking (SCC) and corrosion fatigue by capturing the competing effects of passive film rupture, localized dissolution, and film reformation under mechanical loading. A coupled electro-chemo-mechanical phase-field model is established to simulate localized corrosion and pit evolution under both activation-controlled and diffusion-controlled regimes, with benchmark simulations—including pencil-electrode and semicircular-pit tests—used to validate the model against analytical solutions and experimental observations. The framework is extended to incorporate anisotropic elasticity and crystal plasticity, enabling analysis of corrosion-assisted crack initiation in single-crystal, bicrystalline, and polycrystalline 316L stainless steels. Orientation-dependent corrosion behavior observed in aluminum and other face-centered cubic metals is captured, producing anisotropic pit morphologies consistent with electron backscatter diffraction–based microstructural observations. Comparisons between conventional and laser powder bed–fused 316L microstructures demonstrate that grain morphology, crystallographic texture, and grain boundaries govern corrosion susceptibility and pit-to-crack transitions. An additional contribution is the formulation of a film rupture–dissolution–repassivation cycle that quantifies the cyclic interaction between electrochemical kinetics and mechanical stress through a time-dependent interface mobility, capturing passive film rupture, active dissolution, and repassivation-driven surface healing. Under cyclic loading, the model reproduces the asynchronous coupling between mechanics and corrosion, wherein tensile stresses promote rupture and dissolution, while compressive stresses enhance repassivation and crack closure.