Enhanced high-temperature creep resistance in gradient nanograined Fe-Zr alloy via gradient Zr segregation stabilizing grain boundary

DQ Xu and ZF Huang and H Li and V Turlo and LK Xu and Q Shen and F Chen, MECHANICS OF MATERIALS, 211, 105513 (2025).

DOI: 10.1016/j.mechmat.2025.105513

Fine and ultrafine grains in the gradient nanograined (GNG) structure exhibit low creep resistance. As these grains grow, they will further influence the hetero-deformation behavior when interacting with coarse grains under tensile loading. Solute segregation could be effective for stabilizing nanograins, but the distribution of solute atoms and its influence on the structure-performance relationship in the GNG structure remain unclear. Here, the Zr solute segregation gradient is found energetically favorable in the Fe-Zr GNG alloy based on molecular dynamics simulations, where the solute concentration at GBs shows a gradient distribution across the GNG structure. This dual heterogeneity contributes to improved creep resistance while also retaining the heterodeformation induced strengthening nature of the GNG structure. A pseudo-composite structure is then demonstrated from the dual heterogeneity structure design: the finer grain region with higher segregation concentration, which acts as the thermodynamical stabilizer to enhance creep resistance; and the coarser grain region with smaller segregation concentration, which acts as plastic deformer to provide necessary hetero-deformation accommodation ability. Our work introduces segregation-induced concentration gradient into traditional heterogeneous materials and presents a new route for improving the creep resistance and tensile properties of heterostructure materials.

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