SKM 2021 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 3: Topical Session Interface-Dominated Phenomena - Defect Structures and Mechanical Properties

MM 3.6: Vortrag

Montag, 27. September 2021, 14:30–14:45, H2

Unravelling the lamellar size-dependent fracture behavior of fully lamellar intermetallic γ-TiAl — •Anupam Neogi and Rebecca Janisch — ICAMS, Ruhr-University Bochum, 44780 Bochum, Germany

Strengthening of metals by incorporating nano-scale coherent twin boundaries is one of the important breakthroughs in overcoming the strength-ductility trade-off in recent years. Also, nano-scale twin boundaries in the nano-lamellar in lightweight Ti-Al alloys promise great potential, but their contribution to the deformation and fracture behavior needs to be better understood for designing optimum microstructures. To this end, we carry out linear elastic fracture mechanics informed, large-scale atomistic simulations of fully lamellar γ-TiAl, and find, that nano-scale lamellae are not only effective in improving the fracture toughness and crack growth resistance, but the lamellar size possesses a significant controlling role on the crack tip mechanisms. The fracture initiation toughness exhibits an increasing trend with decreasing lamellar size until ∼3 nm. In this regime, the crack tip events are mostly dislocation-based plasticity. Below the critical lamellar size of ∼3 nm, the crack advances via a quasi-brittle manner, i.e., the cleavage of atomic bonds at the crack tip accompanied by some plasticity events, such as twin-boundary migration and dislocation nucleation. A layer-wise stacking fault energy-based analysis, including the quantitative analysis of dislocation barrier energy, elucidates the nano-scale lamellar size-dependent fracture behavior of γ-TiAl.