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 NbCr 2 , and the vast majority of alloying element Mo is found in the Nb matrix not in NbCr 2 particles. The grain size of Nb matrix exhibits a certain degree of growth during the thermal exposure process, while the grain size of NbCr 2 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 NbCr 2 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 NbCr 2 particles.