Heterogeneous deformation and damage mechanisms in multi-phase TA15 Ti-alloy: Insights from experiments informed damage-crystal plasticity modelling

Understanding the mesoscale heterogeneous deformation and its induced material damage is significant to enhance the mechanical properties of polycrystalline aggregates. In this work, a damage-coupled crystal plasticity finite element (DC-CPFE) model based on high-fidelity microstructure was developed to investigate the heterogeneous deformation and damage behavior of TA15 Ti-alloy with tri-modal microstructure composed of globular alpha (alpha p), lamellar alpha (alpha l) and transformed beta (beta t). A three-step procedure combining the nanoindentation test, stress relaxation test, and uniaxial tensile test was proposed to determine the material parameters in the crystal plasticity constitutive and damage models of the three constituent phases. Based on the developed DC-CPFE model, the heterogeneous slip modes and traces of tri-modal microstructure were predicted and analyzed. The heterogeneous deformation of tri-modal microstructure was found to be mainly caused by the heterogeneous deformation in alpha phases, which was featured by the deformation bands and local shear bands. Deformation bands occurred in both of the deformation-preferential and -lagged alpha p grains and the hard-todeform alpha l grains. Local shear bands only produced in alpha l grains, which were related to both of the soft geometry orientation and the activation of prismatic slip systems. Meanwhile, the formation of deformation bands and local shear bands could be promoted by the local lattice rotation. The above heterogeneous deformation led to four types of damage, which were caused by the slip band intersection, the slip transfer impedance, the local shear band, and the property and orientation mismatches among the adjacent grains, respectively.

Automated summary

Understanding the heterogeneous deformation and damage at the mesoscale is important for improving the mechanical properties of polycrystalline aggregates. In this study, a damage-coupled crystal plasticity finite element model was developed to investigate the deformation and damage behavior of a tri-modal microstructure in TA15 Ti-alloy. Experimental tests and numerical simulations revealed that the heterogeneous deformation was primarily caused by the alpha phases, leading to four types of damage.