In-situ investigation of plasticity in a Ti-Al-V-Fe (α+β) alloy: Slip mechanisms, strain localization, and partitioning

• Origin of strain localization bands was revealed by in-situ strain mapping. • Phase boundary slip transferability was assessed by crystallographic calculations. • Moderate strain partitioning trends were identified between α/β phases. • Correlations between deformation micro-features and damage behavior were recognized. As one of the representative characteristics of plastic deformation, microstructural plastic strain inhomogeneity has triggered a broad interest in uncovering the corresponding deformation micro-mechanisms. (α+β) titanium alloys enable fruitful mechanistic explorations of this dependency, since: (i) the plastic anisotropy of the α-phase drives distinctive dislocation gliding and/or mechanical twinning modes for plastic strain accommodation; and (ii) deformation transferability between α/β phase boundaries strongly relies on both microstructural and structural parameters. The present work carried out in a Ti-Al-V-Fe (α+β) alloy is an in-situ mechanistic study, aiming to elucidate the critical deformation micro-mechanisms that are responsible for strain localization, partitioning, as well as damage inception processes. It is revealed through statistical analysis of the in-situ strain mapping results that a moderate partitioning trend exists between α- and β-phases, and that the present alloy is characterized by the eminent strain localization bands that develop at the early stage of plastic straining. Deformation micro-mechanisms including texture-facilitated prismatic 〈 a 〉 slip activation together with the near-ideal slip transfer conditions across the α/β phase boundaries are found to be predominant in the strain localization regions. The combination of postmortem and in-situ damage analyses confirm the dominant role of these long-range strain localization bands in expediting surface cracking events.