Unlocking anisotropic plasticity in γ-TiAl with an atomic scale simulation: From metastable BCC states to hierarchical twinning

JQ Shi and XL Guo and H Li and LL Li and RH Yin and XL Wang and SF Xu and JJ Lu and J Wang and SW Feng and B Zhao and TF Cao and XL Fan, NANO RESEARCH, 18, 94907894 (2025).

DOI: 10.26599/NR.2025.94907894

Crystal orientation governs the plasticity of intermetallic alloys, yet the atomic-scale mechanisms linking defect dynamics to mechanical properties remain elusive. Here, we unveil unprecedented deformation pathways in single-crystal gamma-TiAl through largescale molecular dynamics simulations under uniaxial tension across four crystallographic orientations: 100, 112, 110, and 111. Strikingly, a metastable body-centered cubic (BCC) phase emerges transiently during 100- oriented stretching, acting as a critical bridge between elastic and plastic regimes-a phenomenon unreported in gamma-TiAl. For 110 and 111 orientations, we identify a hierarchical defect evolution cascade (intrinsic stacking faults-extrinsic stacking faults-twin boundary (ISF- ESF-TB)) driven by intersecting stacking faults and Shockley partial dislocation interactions, which govern twin boundary nucleation and growth. In contrast, 112-oriented deformation adheres to conventional dislocation-mediated plasticity. These findings reveal how crystallographic anisotropy dictates defect dynamics, offering atomic- scale insights into deformation twinning and transient phase transitions. This work bridges atomistic processes to macroscopic properties, advancing the design of next-generation lightweight high- temperature materials.

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