Calibration of crystal plasticity constitutive parameters for γ and α₂ phase in TiAl alloys related to indentation size effect

In this work, an enhanced method for identifying constitutive parameters in TiAl alloys is employed to effectively capture the size effects in the γ and α₂ phases. The results show that significant nanoindentation size effects are observed in both phases, enabling determination of size-independent hardness values of 3.640 GPa for the γ phase and 6.181 GPa for the α₂ phase. An improved calibration approach eliminates errors induced by the indentation size effect (ISE), yielding accurate initial slip resistances: in the γ phase, 305 MPa for ordinary dislocations and 457.5 MPa for super-dislocations; in the α₂ phase, 254 MPa (prismatic slip), 762 MPa (basal slip), and 2286 MPa (pyramidal slip). Increasing Al content from 43 % to 45 % raises the CRSS for ordinary dislocation slip in the γ phase by 38.5 % and markedly increases prismatic <a> slip CRSS in the α₂ phase by 171.9 %. Similarly, increasing Mo content from 0.5 % to 1.5 % elevates the CRSS in the γ phase by 77.0 %, while only a modest increase of 6.9 % occurs in the α₂ phase. The method provides a reliable framework for quantifying microstructure-sensitive mechanical behavior in multi-phase alloys.