Effect of composition on the micro-nano mechanical properties and crystal plasticity constitutive parameters of TNM-based TiAl alloys

This study combines nanoindentation and crystal plasticity finite element (CPFE) simulations to determine the micro-nano mechanical properties and constitutive parameters of γ and α₂ phases in TiAl alloys. Phase-specific parameters were successfully calibrated through inverse analysis, validated by excellent agreement between simulated and experimental curves. Both phases showed orientation-dependent hardness, and the γ phase also exhibited orientation-dependent elastic modulus. The intrinsic size-independent hardness H₀ was determined through indentation size effect analysis. As Al content increases from 43% to 45%, γ-phase hardness rises from 3.470 GPa to 4.625 GPa while α₂-phase hardness increases from 5.801 GPa to 6.734 GPa, with corresponding critical resolved shear stress (CRSS) values increasing by 43% and 50%, respectively. Conversely, increasing Mo content from 0.5% to 1.5% enhances γ-phase hardness from 3.629 GPa to 4.851 GPa but reduces α₂-phase hardness from 7.326 GPa to 6.052 GPa, while similarly elevating CRSS values by 43% and 50%. Further analysis reveals that Al content increase elevates γ-phase elastic modulus by14.3% but reduces α₂-phase modulus by 8.7%, whereas Mo content increase significantly enhances α₂-phase modulus by 2.6% without substantially affecting γ-phase modulus. This integrated approach provides quantitative insights into composition-dependent mechanical behavior of individual phases in TiAl alloys.