Phase-field modeling of implantation rate effect on nano-fracture nucleation in first-wall materials

This work presents a new computational framework to investigate the role of He implantation rate on nano-crack nucleation in molybdenum. The understanding of crack nucleation under He accumulation is especially important for an efficient design of fusion reactor first-wall materials. The framework couples implantation kinetics with defect accumulation dynamics through phase-field modeling and micromorphic stress evolution, enabling a multiscale representation of irradiation-induced damage processes. By systematically varying the implantation rate, we identify its critical influence on crack nucleation thresholds, and the temporal onset of microstructural instabilities. The model captures experimentally observed trends. The results highlight implantation rate as an important factor controlling the balance between defect recombination and accumulation, thereby influencing the initiation of nano-scale cracks. The framework provides a predictive tool to assess material performance under extreme irradiation conditions and serves as a foundation for future extensions incorporating thermal gradients and helium diffusion. This approach advances both the mechanistic understanding and predictive capabilities required for the reliable design of candidate first-wall materials in fusion energy systems.