Regensburg 2019 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 5: Mechanical Properties

MM 5.5: Talk

Monday, April 1, 2019, 11:15–11:30, H46

Molecular dynamics investigation of size effects in lamellar γ-based TiAl alloys — •Ashish Chauniyal, Alexander Hartmaier, and Rebecca Janisch — ICAMS,Ruhr-Universität Bochum

Two-phase γ-based TiAl alloys with a lamellar microstructure are interesting candidates for high temperature structural applications, due to a beneficial combination of creep resistance and fracture toughness. These microstructures consist of the α₂-Ti₃Al and γ-TiAl phases, which can be as finely spaced as several tens of nanometers. The thickness and distribution of these phases in such nano-lamellar alloys is a dominant factor dictating their hardness, which increases with decreasing lamellae spacing. However, nanoindentation tests are limited by the indenter size which indents over several lamellae simultaneously and provides only an averaged value of local hardness. Furthermore, the dynamics in nano scale is hard to capture and is mostly speculative based on pre- and post-indentation images. Using large scale atomistic simulations, indents can be made on individual lamellae using small indenters, which allows us to decouple the individual influence of lamella thickness, spacing and lamella phase on the hardness of the samples. In this study we carry out molecular dynamics nanoindentation simulations to identify the origins of the experimentally observed size effects. Furthermore, we focus on the evolution of dislocation activity underneath the indenter and correlate it with local and average hardness.