Thermal stability of Nb–Cr–Mo alloy

Abstract

The thermal stability of Nb–Cr–Mo alloy with the composition Nb-22.5Cr-2.5Mo (at.%), was studied by thermal exposure experiments in vacuum conditions at 1200 °C for 30 h, 50 h, and 100 h. The phase composition consists of Nb and C15 NbCr2, and the vast majority of alloying element Mo is found in the Nb matrix not in NbCr2 particles. The grain size of Nb matrix exhibits a certain degree of growth during the thermal exposure process, while the grain size of NbCr2 has no obvious change due to its high thermal stability. After thermal exposure at 1200 °C for 100 h, the alloy keeps its higher strength by the solid solution strengthening effect of Mo and the dispersion strengthening of NbCr2 particles. At the same time, it has good plasticity due to dislocation slip in the Nb matrix and the emergence of stacking faults, twins and partial dislocations in NbCr2 particles.