Theoretical study on the effect of element segregation on the dissolution and diffusion of hydrogen at the Ni/Ni3Al interface

Abstract

In this work, employing first-principles calculations, tetrahedral, octahedral, and pyramid-shaped H trap models are constructed to investigate the behavior of hydrogen (H) at the Ni/Ni3Al interfaces with Cr, Mo, and W segregation. Our study reveals that H is prone to adsorb near the Ni3Al phase, forming octahedral H trap structures. Cr segregation H trap is more suitable at the interface, due to the smaller atomic charge of Cr among the three elements, resulting in the lowest dissolution energy required for H dissolution. All the segregation elements exhibit inhibitory effects on H aggregation and segregation, with Mo showing the most pronounced effect due to its highest diffusion barrier. The solubility, diffusion coefficient, and permeability of H at the element segregation interfaces are found to be positively correlated with temperature. Furthermore, the incorporation of segregation elements in the interface trap structure demonstrates a significant enhancement in fracture toughness, while simultaneously mitigating the adverse effects of H on the interface fracture strength. The yield strength and tensile strength exceed those of the original interface. These findings offer theoretical guidance for the design of Ni-based high-temperature alloys with superior performance in the future.