Effects of phase boundary orientation on slip transfer, slip localization, and damage in tension of Ti55511 titanium alloy

This is the authors' abstract. We don't add key points for this paper.

Heterogeneous strain distribution in dual-scale lamellar near-β titanium (Ti) alloys determines early damage sites and crack paths, yet the crystallographic and phase boundary (PB) factors governing this behavior remain unclear. To address this, in-situ electron backscatter diffraction (EBSD) tensile experiments are combined with molecular dynamics (MD) simulations on two ideal grain orientations to systematically elucidate how primary α (α p ) variant orientation, geometric compatibility and α p /β PB orientation control slip activation, transfer, and propagation in bi-lamellar Ti-5Al-5Mo-5 V-1Cr-1Fe (Ti55511) alloy. The MD simulations show that each α p variant accumulates dislocations or develops substructure according to its orientation and PB orientation, following an assumed uniaxial tension deformation boundary condition. In particular, α p /β PBs in 〈100〉 β grains have lower resistance to slip transfer than many in 〈110〉 β grains, which promotes earlier yielding, localized strain concentration, and preferential crack nucleation at 〈100〉 β grain boundaries (GBs). There is good correlation between the simulations and experimental observations. By linking local PB mechanics to macroscopic mechanical response, our work provides a fundamental basis and strategic direction for crystallographic and PB engineering to optimize strain distribution, thereby enhancing the strength-ductility balance in advanced aerospace Ti alloys.