Deciphering the role of macrozones in the microstructure globularization and tensile fracture: Insights from a new developed marine engineering titanium alloy

During the thermal-mechanical processing of titanium alloys, the formation of macrozones is unavoidable within complex components, which significantly degrades their performance. This study systematically investigates the effects of rolling-induced macrozones on the static globularization of the microstructure during annealing. Furthermore, a comprehensive elucidation is provided on the influence of macrozones with different crystallographic orientations on the room temperature mechanical properties of the Ti-Al-Mo-Zr-Nb-V alloy through an analysis of slip activation and transmission. The findings indicate that within the macrozones, static globularization of the microstructure, primarily governed by the boundary splitting mechanism, is hindered due to the similar orientation of the α phase; In the unidirectionally rolled and annealed sheet featuring [0001]//TD macrozones (Type I), distinct deformation mechanisms emerge under rolling direction (RD) and (transverse direction) TD loading, resulting in significantly anisotropic mechanical properties; Conversely, in the cross-rolled and annealed sheet, macrozones characterized by average Euler angles of (155°, 80°, 30°) (Type II) and (175°, 120°, 0°) (Type III) are consistently adjacent to each another, facilitating crack nucleation at the interfaces of macrozones and propagation along the length. The room temperature plasticity of this sheet exhibits nonuniformity, with a wider distribution of macrozones correlating with poorer plasticity. This study will contribute to the advancement of knowledge in this field and aid in the development of improved strategies for controlling macrozones and optimizing performance in titanium alloys.