Assessing the Role of Thermal Gradients in Abnormal Grain Growth of Tungsten Under Fusion-Relevant Conditions

• Developed a coupled phase-field and transient thermal model to simulate tungsten grain growth under fusion-relevant conditions. • Analyzed the effect of zero-flux boundary conditions for a phase-field modeling. • Demonstrated that temperature gradients alone are insufficient to trigger abnormal grain growth (AGG) in tungsten monoblocks. • Utilized tungsten-specific material parameters to isolate and analyze the influence of thermal gradients on microstructural evolution. • Artificially induced AGG using a sharp thermal boundary layer, highlighting that the framework can produce AGG and additional mechanisms are required to explain experimentally observed AGG. Abnormal grain growth (AGG) in tungsten under fusion-relevant heat fluxes threatens the structural stability and lifetime of plasma-facing components. In this work, we employ a coupled phase-field and transient thermal model to evaluate the influence of realistic thermal gradients on grain evolution in tungsten monoblocks. The model is quantitatively calibrated using the thermal loading conditions from the Max Planck Institute’s GLADIS high heat flux campaign, where tungsten monoblock divertor targets were exposed to repetitive heat loads up to 20 MW / m 2 , resulting in localized recrystallization and AGG. The simulations use these experimentally derived temperature fields to isolate the role of thermal gradients in driving grain boundary migration. The results show that realistic EUROfusion DEMOnstration power plant (DEMO), gradients significantly enhance grain coarsening but do not independently trigger AGG, indicating that additional physical mechanisms, such as strain accumulation or impurity drag, are required to reproduce the experimental observations. This insight provides a physics-based foundation for mitigating AGG in fusion-relevant tungsten components and supports predictive microstructural design for improved durability.