Abstract
<title>Abstract</title> <p>Developing stronger alloys is essential for structural applications, but their reliability is limited by brittle cracking along general grain boundaries (GGBs). Solute segregation can control grain-boundary fracture, yet its effects are typically interpreted in terms of static cohesion changes before and after interfacial separation. How trace solutes modify moving-crack resistance at GGBs remains unclear because realistic segregation and crack propagation are difficult to treat atomistically. Here, we develop a fast and transferable Fe–C machine-learning interatomic potential. Using simulations of experimentally consistent carbon-segregated α-Fe GGBs, we show that trace carbon markedly increases crack-growth resistance, consistent with observed transition from intergranular fracture to cleavage. Carbon follows the moving crack tip through repeated breaking and reforming of Fe–C bonds, enriching the crack-tip region. We term this process dynamic bond reconfiguration (DBR). DBR dynamically amplifies static cohesive strengthening, revealing dynamic solute–crack-tip interactions as a framework for controlling brittle fracture in alloys.</p>