2026/07/17 by Sadia Khan, Hamdy Arkoub, Miaomiao Jin
#cond-mat.mtrl-sci
Corrosion of Ni-Cr structural alloys in molten fluoride salts is a persistent material degradation problem, yet the atomistic role of grain boundaries in this process remains poorly understood. Here we use reactive molecular dynamics to investigate corrosion of NiCr alloys in molten FLiNaK across four representative grain boundaries (Σ3(111), Σ11(113), Σ5(012), and Σ5(013)) and corresponding bulk surfaces. Surface crystallography controls the initial dissolution stage, while grain boundary character governs the spatial localization and longer-time evolution of corrosion. We further identify a corrosion-driven grain boundary migration mechanism in which fluorine localization, preferential chromium dissolution, and vacancy-mediated mobility together drive interfacial motion away from the dealloyed region. The coherent Σ3(111) boundary suppresses these processes, indicating low-energy special boundaries as targets for grain boundary engineering of corrosion-resistant Ni-Cr alloys.