TECHNICAL: The project aims to design a complete new class of high temperature Ti-Al-Nb-based alloys for gas turbine components (blades and vanes) operating under harsh environmental conditions. The objectives of this project are to develop a mechanistic understanding of phase transformation and reactions in Ti-Al-X-Y systems with the aim of developing two-phase alloys with optimized high temperature creep properties and fracture toughness. Based on PIs' previous work on Ti-Al-Nb alloys, they will undertake a unique alloy development approach for precipitation hardening of TiAl alloys with another intermetallics phase as the hard second phase. These new alloys will consist of a gamma-TiAl(Nb) matrix reinforced by submicron-sized sigma-Nb2Al precipitates. Advanced software and phase modeling will be applied to simulate the complex multi-component multiphase alloy solidification paths and phase reactions. From these data, guidelines for alloy heat treatments (homogenization, ageing) will be derived and the experiments can be efficiently focused to the final optimization of the microstructure of the alloys. The mechanical properties of the most promising alloys will be tested. The investigations include the study of the micro-hardness and fracture toughness as well as tensile tests and creep experiments at room temperature and elevated temperatures. Electron microscopy will be used to analyze the mechanisms of deformation and fracture. These results will be used to select an alloy composition and fine tune the microstructures for enhanced properties. The intellectual merit of the research activity is an innovative and knowledge-based alloy development using a combined theoretical/experimental approach: the simulation results of computational thermodynamics in the Ti-Al-X-Y (X=Nb, Mo; Y=Ta) system will be used to guide the experimental work for the microstructure optimization. The PIs are experts in both computational thermodynamics and experimental investigation of metallic alloys. NON-TECHNICAL: This approach will be highly efficient for the alloy development and helps to avoid trial-and-error experiments. From earlier work of the principal investigators it can also be expected that such alloys can be produced at much lower costs compared to the standard (single-crystal) Ni-base superalloys. The broader impacts of these activities include the training and teaching of students in an efficient and innovative alloy development by using simultaneously computer simulation methods and well-selected experiments. The results of this work will be published in international peer-assessed journals, conference presentations and proceeding papers. The PIs will recruit students from under-represented groups to work on this project. The MSE department at UF is one of the largest departments in the country, and has an exemplary record in educating under-represented groups.
