Size-dependent deformation mechanisms in two-phase γ-TiAl/α2-Ti3Al alloys
Shiping Wang, Xiong Zhou, Zhongtao Lu, Xiege Huang, He Li, Xiaobin Feng, Wenjuan Li, Pengcheng Zhai, Guodong Li
Abstract
Polysynthetic twinned (PST) TiAl single crystals, consisting of alternating layers of γ-TiAl and α 2 -Ti 3 Al, exhibit excellent mechanical properties. However, size-dependent deformation mechanisms have not yet been fully elucidated. In this work, we investigated the deformation process of two-phase γ-TiAl/α 2 -Ti 3 Al alloys with different layered sizes via uniaxial tensile loading using molecular dynamics simulations. The results show that with the decreasing phase boundary (PB) spacing λ or domain boundary (DB) spacing d , the excess free volume at the intersection of DB and PB decreases, leading to increased yield stress. We found that a higher interface density (smaller λ or d ) can accommodate more dislocations, and the size-dependent ultimate strength follows an approximate Hall-Petch relation. These findings offer an essential understanding for the size-dependent PST TiAl single crystals with high strength.