Deformation mechanism transition and ductility enhancement in Ti-55531 alloy under combined pre-torsion and tension loading

The effects of varying pre-torsion amounts (35 and 41 N·m) on the tensile properties, deformation mechanisms, and fracture behavior of Ti-55531 alloy with a bimodal microstructure were investigated using a combined pre-torsion and tension loading approach. The findings reveal that pre-torsion deformation prior to tension enhances the activity of plastic deformation mechanisms by promoting dislocation slip and altering grain orientation. Under uniaxial tensile loading, the α p phase activates multiple prismatic slip planes without significant interaction. Conversely, under pre-torsion (35, 41 N·m)−tension loading, the α p phase predominantly induces interactions among multiple slip planes within the prismatic slip system, resulting in an increased density of slip lines as the pre-torsion amount increases. Furthermore, pre-torsion promotes the formation of high-density twins within a single α s lath following tensile deformation.