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Multiscale modeling of lattice dynamical instability in gamma-TiAl crystal
K. Xiong, X. Liu, J. Gu
Keywords: titanium aluminide, multiscale modeling, nanoindentation, lattice instability, dislocation nucleation
Abstract: In this paper, the lattice instability of γ-TiAl crystal under different loading modes was studied using a lattice dynamical finite-element method (LDFEM) and molecular dynamics (MD). The simulation results show that the lattice instability of γ-TiAl crystal is significantly influenced by loading modes and crystallographic orientations. In uniaxial loading, γ-TiAl crystal exhibits tension-compression asymmetry in critical stress. The stress–strain curves and the active slip systems obtained from LDFEM simulations are in agreement with those in MD simulations. In the nanoindentation of γ-TiAl crystal, surface orientation plays an important role in stress field, lattice instability and dislocation nucleation. The LDFEM accurately predicts the location of lattice instability and the active slip systems. The surface effect on lattice instability in nanoindentation was also proved by performing a cylindrical nanoindentation.
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