Unveiling the superior high-temperature mechanical property of molybdenum single crystal by adding Nb element

In the present work, the molybdenum alloy single crystal has been deformed at both high temperature and high strain rates. The microstructure evolution of the pure Mo and Mo[sbnd]Nb single crystals subjected to the dynamic load at 800 °C was investigated by EBSD and TEM. The mechanical curves show a V-shaped characteristic and a strain rate sensitivity. With the increase of strain rate and Nb content, the curves gradually become smooth and the V-shape characteristics disappear. The pure Mo and Mo[sbnd]Nb alloy single crystals still maintain the single crystal structure at strain rates ranging from 1500 to 2500 s⁻¹. At a strain rate of 2500 s⁻¹, the deformation is dominated by dislocation slip, and with the addition of Nb element, the dislocation configuration changes the dislocation wall of pure Mo single crystal to the dislocation cell with the high-density dislocation entanglement of Mo[sbnd]3Nb single crystal, and finally to the uniform dislocation cell of Mo[sbnd]6Nb single crystal. This work provides a new idea for the processing and composition design of refractory alloy single crystals.