Work

Atomic investigation of the critical role of niobium in irradiation-induced hardening of molybdenum-niobium alloys

Year: 2026

Type: article

Abstract: Molybdenum-niobium (Mo-Nb) alloys are regarded as the preferred materials for energy conversion components in space thermionic reactors due to their excellent creep resistance and low work function. However, the fundamental mechanism of irradiation hardening induced by solute Nb atoms remains elucidated. Here, the interaction between edge dislocations and Nb-decorated irradiation-induced defects was investigated by employing molecular dynamic (MD) simulations, and results were compared to those of interacting with irradiation-induced defects and Nb-rich clusters. Simulation results demonstrated that the aggregation of Nb on loops significantly influences the interaction between these loops and edge dislocations. The loops can be converted from weak barriers to strong obstacles by Nb atoms decorated, and this transformation is particularly pronounced when loop orientation is parallel to the glide plane and simultaneously inclined relative to the Burgers vector of the interacting dislocation. The pinning strength of Nb-decorated loops on gliding dislocations also relates to Nb concentration. Once the Nb concentration exceeds a specific critical value, the loops can no longer be absorbed or chopped up by the gliding dislocations. Furthermore, the critical Nb concentration exhibits an upward tendency as loop size increases, which can be attributed to the reduction in the average binding strength between Nb atoms and loops within the Mo matrix as loop size grows, and a higher Nb concentration is thus required to counteract this decline in binding strength. These findings provide novel insights for a deep understanding and a rational explanation of the intrinsic mechanism of irradiation hardening in the Mo-Nb system.

Source: Nuclear Materials and Energy

DOI: 10.1016/j.nme.2026.102104