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MM: Fachverband Metall- und Materialphysik
MM 64: Mechanical Properties: Plasticity, fracture, fatigue, wear - II
MM 64.5: Vortrag
Donnerstag, 19. März 2020, 18:30–18:45, IFW B
Effect of lattice misift on the deformation behaviour of two-phase lamellar TiAl alloys — •Ashish Chauniyal and Rebecca Janisch — ICAMS, Ruhr Universit
"at Bochum
Deformability and strength of two phase TiAl alloys strongly depends on the presence of different interfaces in their microstrucure. Two phase TiAl alloys consists of face centered tetragonal γ(TiAl) phase and hexagonal α2(Ti3Al) phase. The interfaces in lamellar alloys are either γ/γ or α2/γ. Lattice misfits arise due to different crystal structures at α2/γ interface or due to tetragonality at γ/γ interfaces. A coherent interface, with matching lattice points, leads to coherency stresses in lamellae, whereas a semi-coherent interface has misfit dislocations. Using molecular dynamics simulations we study the deformation behaviour of coherent and semi-coherent interfaces by carrying uniaxial tensile tests on bi-layer specimens of α2,γ. We quantify the relation between volume fraction and coherency stresses in lamellae and distinguish the role of volume fraction and individual lamellar size on deformation behaviour. Coherency stresses in lamellae lead to early yielding of α2,γ bilayers which could be the origins of the observed microplasticity in TiAl alloys. Furthermore, we show that misfit dislocations at the interfaces create local stress fluctuations within the lamellae, which in turn, lead to dislocation nucleation. Thus, we distinguish different dislocation nucleation mechanisms in coherent and semi-coherent interfaces in correlation with changing stress states caused due to lattice misfit.