Physics and Mechanism-based Predictive Modelling of Plastic Deformation and Fracture in Ti and Ti-6Al-4V Alloy
DescriptionTitanium (Ti) alloys are widely used in light weight, high strength and high resistance to corrosion applications. They have strategic importances in the aerospace, energy and biomedical industries. Despite their importances, the grain-scale defects, microstructures and their interactions in Ti are not well understood, even though they control material strengthening, hardening, fatigue and fracture.The proposed research aims to quantitatively establish the grain-scale materials science and mechanics of hexagonal close-packed (HCP) Ti and dual-phase HCP/body-centered cubic (BCC) Ti- 6Al-4V (Ti64) alloy by (i) determining their defect properties and solute chemistry at the accuracy of quantum mechanics; (ii) developing accurate atomistic potentials capable of reproducing defect properties and solute chemistry; (iii) investigating the mechanisms of plastic deformation and fracture; and (iv) developing physics and mechanism-based, predictive models capturing the essential materials science and mechanics of Ti. The proposed research uses a sequential multiscale approach spanning quantum, atomistic and micro mechanics scales. First, fundamental defect properties and their interactions with Al and V solutes will be rigorously calculated using density functional theory, thereby forming the Material Genome of Ti. Secondly, based on the above Material Genome, accurate empirical/semi-empirical interatomic potentials will be developed using new formalisms of the Multistate Modified Embedded Atom Method and/or Neural Network potentials, thus overcoming limitations of all previous models. Success will enable realistic simulations of defects and microstructures in Ti and Ti64 at atomistic details, and thus represents significant advances in Ti science. Thirdly, the micromechanics of defects, including dislocations, twins, interfaces and their interactions, will be investigated in atomistic simulations using developed potentials. With that, the effects of temperature, stress and strain, microstructure and alloying on material plasticity and fracture will be quantitatively determined. Finally, mechanism-based predictive models will be developed to capture the essential materials science and mechanics obtained from the above quantum, atomistic and micromechanics scales. Such predictive models can guide designs of new Ti alloys and serve as inputs to mechanism-based, finite element models at engineering scales.The proposed research integrates state-of-the-art computational material models and theory, and leverages the latest breakthrough in HCP Mg alloys. Knowledge gained in each scale will advance both fundamental science and engineering designs of Ti alloys. The research program, combining quantum, atomistic and micro mechanics, thus enables the transformation of the empirically-driven, descriptive metallurgy to physics-based, predictive science.
|Effective start/end date||1/01/20 → …|