Loading-mode and Al-content effects on incoherent basal-prismatic boundary migration in Ti-Al Alloys

H Zhang and WZ Li and HZ Cui and J Gu and M Song, INTERNATIONAL JOURNAL OF MECHANICAL SCIENCES, 305, 110735 (2025).

DOI: 10.1016/j.ijmecsci.2025.110735

In hexagonal close-packed (HCP) metals, basal-prismatic (BP) boundaries initially accommodate plastic deformation but later induce strain/stress concentration upon coherency loss. Although their migration alleviates localization, the underlying atomic-scale mechanisms remain elusive. This study unveils the atomic-scale mechanisms governing incoherent BP boundary migration in Ti-Al alloys through molecular dynamics (MD) simulations, addressing a critical gap in understanding strain localization mitigation strategies for hexagonal close-packed metals. Systematic investigations reveal distinct deformation pathways under different loading modes: tensile loading preferentially activates TDs b(2 )()glide in coherent segments, enabling rapid interface expansion through Frank partial dislocation separation and -type defect dissociation in incoherent zones. Conversely, compressive loading induces structural reorganization via TD b(2)() rearrangement and dislocation emission, forming coherent serrated boundaries and dislocation walls. The work further demonstrates how Al alloying uniquely modulates boundary dynamics through dual mechanisms - interfacial stabilization via solute drag and crystallographic transformation promotion by reducing basal stacking fault energy and lowering HCP -> FCC phase barriers. Crucially, Al facilitates interfacial defect transitions to FCC structure while preserving the fundamental migration mechanism. These findings provide fundamental insights into defect-mediated interface evolution mechanism in Ti alloys, with broad implications for designing advanced HCP metallic systems.

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