Abstract
Fully lamellar TiAl alloys are increasingly used as structural materials for high temperature
applications e.g. for turbine blades in low-pressure stages of aircraft engines.
These structurally demanding applications necessitate precise knowledge of the materials
thermomechanical behavior to ensure safe operation.
The numerous microstructural interfaces in fully lamellar TiAl alloys give rise to three
concurrently acting Hall-Petch effects which collectively induce their high strength. So
far, their relative contributions could not be separated uniquely in experiments.
The thermomechanically coupled crystal plasticity model, presented in this contribution,
enables to overcome this experimental limitations and helps to separately quantify the
three different Hall-Petch effects using literature experimental results. This micromechanical
model reflects the morphology of the lamellar compound in a single colony, i.e.
on micro scale, and captures its complicated hardening behavior up to 10% plastic strain.
Subsequently, this micro scale model is transferred to a meso scale polycolony RVE in
order to get insight into the complex interrelations between the different microstructural
strengthening effects.
The model nicely captures the micro yield and micro hardening in fully lamellar microstructures
and the extracted Hall-Petch slopes help to explain the spread in reported
experimentally determined values.
