Capturing Hydrogen Embrittlement Effects with Hydrogen Diffusion Simulation and Crystal Plasticity

Abstract

Hydrogen is a promising clean energy source, but its safe storage is challenging, as hydrogen has severe embrittling effects on metals. The extent of hydrogen embrittlement depends on the local hydrogen concentration and how it couples with the thermal and structural counterparts. This work presents a framework for hydrogen diffusion and embrittlement effects considering underlying microstructure. A hydrogen diffusion simulation is conducted on a microstructure with grain boundary trap** effect and trap** site saturation effect explicitly considered. The simulation provides a time history of hydrogen concentration in the microstructure. The grain boundary decohesion and softening effects of hydrogen are described phenomenologically by a nonuniform initial slip resistance degradation, which is computed based on the hydrogen concentration profile. This initial distribution is then used in crystal plasticity simulations to predict how the hydrogen exposure affects the mechanical properties such as initial yield stress and subsequent flow behavior. The results show that the diffusion model can capture the trap** effects of hydrogen as well as the gradual saturation of trap** sites with increased hydrogen concentration. The phenomenological model for hydrogen-based slip resistance degradation is able to capture the increased softening with longer hydrogen exposure times. The current framework provides a simple yet effective framework to connect microstructure-informed diffusion simulation with crystal plasticity to quantitatively study hydrogen embrittlement.