New insights into the recrystallization behavior of large-size Mo-3Nb single crystal based on multi-scale characterization

The occurrence of recrystallization will cause catastrophic damage to the structure of metallic single crystal, which can be avoided by choosing crystal orientation reasonably. In this work, the effect of crystal orientation on the recrystallization behavior of single crystal is investigated using multi-scale characterization method. The electron backscattered diffraction analysis shows that in mesoscopic scale, the recrystallization behavior of Mo-3Nb single crystal exhibits a strong orientation dependence, which the new recrystallization grains are produced in the <111>-oriented single crystal, while the single crystal structure is still retained in other orientations. At the micro scale, the elongated dislocation cells with certain misorientations appear in the <111>-oriented single crystal, while only the dislocation walls and parallel dislocation cells distribute on the single crystal with the <110> and <112> orientations, respectively. The length of dislocation lines in deformed single crystal with <111> orientation is calculated using molecular dynamics to be 3491.22 Å, which is much longer than that of the <112> orientation (1133.27 Å) and the <110> orientation (2862.68 Å), suggesting a higher crystal distortion and easier recrystallization in the <111> orientation. In addition to the coalescence mechanism of discontinuous sub-grains, the shear band also plays an important role in promoting recrystallization nucleation. This work provides reference value for the secondary processing of molybdenum single crystal, so as to obtain more excellent products and expand its potential application.