Improved creep resistance of a nanograined Fe-Ni alloy through a diffusional phase transformation mechanism

Huang R.; Kou Z.; Tang S.; Wu S.; Lai Q.; Zhang W.; Chen X.; Lan S.; Wilde G.; Feng T.

Abstract

Grain boundaries (GBs) are known to contribute to the strengthening of metallic materials but often degrade creep properties, resulting in low creep resistance of nanograined (NG) alloys even at room temperature. In this study, we synthesized a NG Fe-Ni alloy using inert gas condensation (IGC), which demonstrated significantly enhanced creep resistance while maintaining a stable grain size after annealing at 300 °C for 1 hour. Microstructural analyses, including synchrotron X-ray diffraction, transmission electron microscopy, and atom probe tomography, revealed that the enhanced creep resistance is attributed to a diffusional phase transformation at the GBs. This transformation drastically reduced the number of stored dislocations, presenting a novel and promising approach for improving the creep resistance of NG alloys.