β-Nb is a typical second phase in Zr-Nb-based alloys used as fuel claddings in water-cooled nuclear reactors.The segregation of alloying element Fe may affect the corrosion resistance of Zr-Nb-based alloys.In this work,the Fe segregation at the interface between β-Nb phase and α-Zr matrix in Zr-2.5Nb alloy was studied using atom probe tomography and focused ion beam.The results suggested that the Fe concentration was much lower than Nb concentration in α-Zr matrix,while Fe selectively segregated at the β-Nb/α-Zr phase interface,leading to a Fe concentration peak at some interfaces.The peak Fe concentration varied from 0.4 to 1.2 at.％ and appeared at the position where Zr concentration was approximately equal to Nb concentration.The selective segregation of Fe should be affected by the heat treatment and structure defects induced by cold rolling.