SKM 2021 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 5: Topical Session Interface Dominated Phenomena - Poster

MM 5.5: Poster

Dienstag, 28. September 2021, 10:00–12:45, P

On the role of rotational twin boundaries in lamellar TiAl on the deformation behavior — •Ashish Chauniyal and Rebecca Janisch — ICAMS, Ruhr-University Bochum, 44780 Bochum, Germany

Twin boundaries in lamellar TiAl alloys have a determining influence on their mechanical properties. During deformation, the twin boundaries prevent easy glide of dislocations, thereby contributing to strengthening. In nano-scale lamellae, twin boundaries can cause considerable dislocation pileups which contribute to strengthening, but compromise ductility. To maintain deformability, it is desirable to have movement of dislocations and sufficient dislocation sources to nucleate new dislocations. In this regard, the twin boundaries in lamellar TiAl are special as the tetragonality of the γ phase (L1₀) leads to several variants of rotational twin boundaries by rotating in steps of 60^∘ around the [111] axis. While a γ/γ_180^∘ boundary is fully coherent, γ/γ_60^∘ and γ/γ_120^∘ boundaries exhibit a lattice misfit at the interface, which can result in coherency or semi-coherency. For a coherent interface a residual coherency stress is generated within the lamallae which can have a profound influence during deformation. For a semi-coherent interface, misfit dislocations at the interface can act as nucleation sources. In this work we model these interfaces atomistically and compare their deformation behavior by carrying out large scale atomistic simulations. Our simulations reveal the mechanisms of dislocation nucleation and propagation in lamellar layers with rotational twin boundaries.