Plastic Strain Inhomogeneity in (α+β) Titanium Alloys—A Focused In Situ Exploration of Transformed β-Colonies

(α+β) titanium alloys demonstrate diverse microstructural combinations that enable fruitful pathways to engineer the macroscopic load-bearing performances. The microscopic deformation mechanisms leading to plastic strain inhomogeneity are, on the other hand, rather complex and deemed detailed considerations. Transformed β-colonies are one such example. Exhibiting a Burgers orientation relationship (BOR) between the BCC-structured retained β-phase (β_r) and the HCP-structured transformed β-phase (β_t), the transformed β-colonies have triggered appreciable interest in correlating slip activation and its crystallographic properties that can be relevant in microstructural design. By studying a Ti-Al-V-Fe-Sn alloy via integrated <i>in situ</i> SEM-based DIC, <i>in situ</i> synchrotron X-ray diffraction, and crystallographic theory, this presentation aims to address three fundamental aspects of the transformed β-colonies: (1) What is the critical factor that dominates plastic strain accommodation in different β_t variants? (2) What are the characteristics of plastic strain partitioning between β_r and β_t phases? (3) How does the BOR contribute to slip transferability across the β_r/β_t boundaries? Broader implications for cooperative and heterogeneous plastic deformation and their roles in damage initiation will also be discussed.