The Mechanical Response of a α2(Ti3Al)+γ(TiAl)-Nanograined Al2O3 Cermet Under Dynamic Compression: Modeling and Experiment

Abstract

Novel experimental data, obtained using an advanced digital image correlation technique coupled to ultra-high-speed photography, have been used to develop and validate a microstructure-dependent constitutive model for α2(Ti3Al) + γ(TiAl)- nanograined Al2O3 cermet. Utilizing experimental characterization for important simulation inputs (e.g., microstructural features size, constituent stiffness), the numerical model makes use of a variational form of the Gurson model, based on the nonlinear homogenization approach, to account for the experimentally observed deformation features in this composite (e.g., void deformation and growth, particle fracture). By considering the variability in microstructural features (e.g., particle shape, size, and aspect ratio), as well as densely packed ceramic particles, the proposed model is evaluated by comparing the numerical responses to experimental results for quasi-static and dynamic stress-strain behavior of the material. The results show that the proposed approach is able to accurately predict the mechanical response and deformation of the microstructure. Once validated, the model is expanded for studying the predominant damage mechanisms in this material, as well as determining important mechanical response features such as transitional strain rates, flow stress hardening, extensive flow softening, and energy absorbing efficiency of the material as a function of void and particle volume fraction under high strain rate loading. The totality of this work opens promising avenues for qualitative (damage micromechanisms) and quantitative (stress-strain curve) understanding of ceramic-metal composites under various loading conditions, and offer insights for designing and optimizing cermet microstructures.