Place: DPG Spring Meeting 2013, Regensburg, Germany
Mechanical properties of different interfaces and bulk structures in the fully lamellar TiAl two-phase system are investigated by an ab-initio DFT (Density Functional Theory) based study with full relaxation. Interfacial energies as well as planar fault energies for γ/γ, α2/γ interfaces and bulk structures are calculated. The tensile strength and cohesive properties for different variants are obtained from implementation of atomic scale uni-axial mechanical test. The remarkable finding is that all interfaces as well as bulk phases have comparable normal strengths. Furthermore, shear properties of the single crystals as well as interfaces are investigated on the basis of generalized stacking-fault energy surface and then the shear strength is calculated along various directions. The results show that 60°-rotated and 120°-rotated γ/γ interfaces display an easy shearing configuration; especially the [-1-12]γ direction shows an invariant and low shear strength for all cases. Our results are discussed and interpreted on the basis of the atomistic configurations of the investigated systems.