Multi-scale analysis of damage mechanisms in high niobium and nitrogen nickel-based alloy

A wide and thick plate of nickel-based alloy enriched with niobium and nitrogen, developed for core equipment in photovoltaic polysilicon production, was produced for the first time using a straight-arc continuous casting machine. However, it exhibits strong crack susceptibility in the solidification mode of continuous casting. Using in-situ high-temperature SEM tensile tests, the precipitates-induced damage processes of the as-cast structure were directly observed. Our observation revealed that the alloy's high crack sensitivity stems from fragmentation of irregular NbN precipitates. A multi-scale finite element and density functional theory framework was established to simulate the damage modes. By integrating the first-principles behavior of particles into a two-dimensional representative volume element model validated by experimental data, the analysis using the developed framework achieves strong agreement between simulations and observations. Results highlight that shape and size of the precipitates, and loading orientation dictate grain boundary failure modes and their roles in crack nucleation and propagation. Furthermore, a novel criterion quantifying crack sensitivity in precipitation-strengthened alloys was developed, offering a method to assess particle-induced crack sensitivity and predict failure mechanisms.