Modelling of fracture of single crystal lamellar TiAl alloys using a two-scale finite element approach

Fracture in lamellar structure of a TiAl single crystal (known as PST crystal) has been modelled using two-scale finite element modelling approach including cohesive fracture behaviour. In this approach the representative microstructure of two-phase lamellae has been simplified in a unit cell model. The lamellar fracture, which can be interlamellar and translamellar type, has been described in the unit cells where the underlying debonding and cleavage mechanisms have been captured using cohesive damage behaviour. The macroscopic response of material failure has been calculated from the lower scale unit cell deformation and fracture behaviour. Stress-strain behaviour of undamaged state has been calculated using first order homogenization approach and the damaged behaviour has been calculated averaging the local stress-strain evolution at the damage zone after the onset of cracks as described by cohesive model. In this work we will demonstrate the proposed modelling approach for capturing micro-meso fracture with numerical examples. In addition, the cohesive model parameters for interlamellar and translamellar fracture will be estimated fitting the model response to the experimental obtained data for single crystal tensile fracture behaviour of a TiAl alloy