Slip-twinning interdependent activation across phase boundaries: An in-situ investigation of a Ti-Al-V-Fe (α plus β) alloy

Microstructural plastic strain distribution evolution is highly heterogeneous even in single-phase alloys. One of the important factors that govern this heterogeneity is slip/twinning transfer across grain/phase boundaries. In this regard, the fundamentals of transfer across grain boundaries have drawn significant attention in the literature, while the understanding of phase boundaries remains comparatively limited. (alpha+beta) titanium alloys provide a profound platform to explore these phenomena, since: (i) both of the present phases can exhibit plastic deformation at similar microscopic strain levels; and (ii) both dislocation slip and mechanical twinning can be triggered to accommodate plastic strain. In the present work, we evidenced a deformation transfer unit involving dislocation slip in the beta-phase and {10 (1) over bar2}-mechanical twin in the alpha-phase. We revealed by crystallographic calculations that the combination of Schmid factor and the Luster-Morris compatibility factor enables a rational quantification for the inception propensity of the slip-twinning transfer event. Our in situ strain mapping approach verified that this sort of transfer activity can plausibly alleviate strain incompatibility/localization, demonstrating the potential to facilitate deformation homogeneity. (C) 2020 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Automated summary

Microstructural plastic strain distribution evolution is highly heterogeneous even in single-phase alloys. The transfer of slip/twinning across grain/phase boundaries plays a crucial role in governing this heterogeneity. Understanding of the fundamentals of transfer across grain boundaries has received significant attention, while knowledge about phase boundaries remains relatively limited.