Insight into the multi-hierarchical interactions between α and β phases during hot deformation of near-β titanium alloy

Hot working of titanium alloys within the (α+β) field is characterized by inherent multi-hierarchical heterogeneous deformation, with the two phases exhibiting distinct deformation characteristics while mutually influencing each other. In this study, systematic uniaxial isothermal compression experiments and crystal plasticity finite element modeling considering morphological characteristics were employed to deepen our understanding of the interactions between α and β phases during hot deformation. The impact of α deformation on the β phase was found to be closely associated with its morphology, distribution, feature size and α/β interface relationship. Primary equiaxed α grains exerted a double-edged effect on the deformation of the β phase. The activation of cross-slip in the β phase, coupled with the predominant pinning effect at β grain interior, collectively resulted in relatively homogeneous plastic deformation in the β phase. This elucidated limited β grain refinement observed in the equiaxed microstructure. Multiple deformation mechanisms in the lamellar microstructure were comprehensively analyzed by considering the active slip systems, slip transfer across phase interfaces and inter-colony interactions. Discrepancies in the activation of slip systems and slip transfer across α/β interfaces led to deformation heterogeneity at the lamellae scale. Notably, lamellar kinking manifested a synergistic effect in accelerating substructure formation in α and β phases. Interactions between colonies induced intense deformation gradients across the colony interface and thus triggered localized dynamic recrystallization, which was highly dependent on the relative orientation relationship of neighboring colonies. Heterogeneous deformation of the lamellar microstructure demonstrated great potential for refining microstructure and weakening microtexture in the β phase. This work offers fresh insights into the intricate interactions between α and β phases during hot deformation, providing a foundation for optimizing the thermomechanical processing of titanium alloys.