The intricacies of α-β microstructures in titanium alloys: Insights into α-phase variant spatial distribution and orientation

Dual-phase α-β titanium alloys are crucial for various titanium applications. This study examines the spatial distribution of α-phase variants in two commercial-grade titanium alloys (Ti-6Al-2Sn-4Zr-2Mo and Ti-6Al-4V), uncovering previously unreported important microstructural features. Key findings include: (i) parallel α-laths observed in two-dimensional (2D) images can originate from distinct α-phase variants, complicating traditional methods of colony classification; (ii) each α-phase variant approximately follows the {11 11 13 ‾ } plane traces of its prior-β grain, providing a unique approach to investigating the configuration and spatial distribution of α-phase variants; and (iii) the dihedral angle between the broad faces of two α-phase variants deviates from their misorientation angle, yet a clear relationship exists between variant orientations and misorientation characteristics. These findings enhance our understanding of α-β Ti alloy microstructures, underscoring the critical need for precise characterization and elucidation of their complex features.