Revealing the orientation dependence of large-size BCC molybdenum alloy single crystal deformed at a high temperature

The orientation dependence of the high-temperature mechanical behavior of BCC Mo-Nb alloy single crystals was reported in this work. The monocrystalline structure is retained after a hot deformation for Mo-Nb single crystal with three orientations, while the mechanical behavior exhibits a significant difference. The entangled dislocation is distributed in the < 112 > orientation and shows a continuously increasing flow stress. However, the deformation microstructure is dominated by dislocation cells and a bit of dislocations within the cells in the < 111 > and < 110 > orientations, where the flow stress remains dynamically balanced. This indicates that the orientation dependence of the high-temperature mechanical behavior is determined by the evolution characteristics of the substructure. The high geometrically necessary dislocation density and low Schmid factor are the main reasons for the dislocation entanglement in the < 112 > orientation, which is rarely reported in body-centered cubic refractory metal single crystal deformed at a high temperature.