Quasi-in-situ investigation on microstructure evolution and structural stability of Mo-Nb alloy single crystal during high temperature creep

The high-temperature creep behavior and microstructural evolution of Mo-Nb single-crystal was investigated at 1650 °C and 30 MPa through quasi-in-situ creep interruption experiments. Creep test results indicate that increasing Nb content from 3% to 6% significantly reduces the steady-state creep rate and prolongs the steady-state creep stage, and the creep resistance of Mo-Nb single-crystal is effectively enhanced. The crack initiation and localized damage is suppressed due to the solid solution strengthening of Nb element. EBSD results further confirm that high Nb content markedly suppresses lattice rotation, sub-grain formation, and dynamic recovery, enabling Mo-Nb single crystals to maintain a monocrystal structure under high-temperature loading. This study elucidates the effect of Nb content on the creep resistance mechanism of Mo-based single crystals, providing a basis for designing high-temperature structural materials for space nuclear reactors.