Microstructure and defect controlled additive manufacturing of gamma titanium aluminides for function-based control of local materials properties

• Applicants: Professor Dr.-Ing. Christoph Leyens; Professor Dr.-Ing. Frank Walther
• Subject Area: Metallurgical, Thermal and Thermomechanical Treatment of Materials ; Mechanical Properties of Metallic Materials and their Microstructural Origins
• Term: from 2018 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 404665753

The superior target is to understand the fundamental relationships between process parameters, solidification and cooling conditions and the microstructure formation and to systematically investigate its impact on the deformation and fracture behavior in additively manufactured gamma-titanium aluminides. Due to a comprehensive microstructure analysis with light and scanning electron microscopy by using EDX and EBSD detectors, X-ray computer tomography, high temperature XRD and instrumented hardness mappings, a fundamental understanding of the relationships between process parameters and microstructure formation will be reached. In contrast to past studies, different microstructure formations can be generated by usage of different energy sources (laser and electron beam) as well as in- and post-process heat treatments (induction, HIP, aging, solution annealing) at IfWW. For this purpose, the basic parameters (scanning speed, deposition rate, substrate temperature) as well as the influence of different building directions (vertical, horizontal) will be investigated. Simultaneously, a fundamental analysis of the fatigue deformation and fracture behavior and a correlation of the microstructure characteristics with the fatigue properties will be allowed due to a further development of the mechanism-based testing methodology of WPT for a resource-efficient characterization of the fatigue behavior of gamma-titanium aluminides at room and high temperatures. Especially, the continuously transfer of the results in correlation matrices in order to realize a model-based description of the fundamental relationships between microstructure and properties will enable a transformation of the research results to additively manufactured gamma-titanium aluminides in industry.Scientific topics and goals:Christoph Leyens, IfWW (1st applicant) • Investigation of influence of different process parameters, e.g. atmosphere (vacuum, inert gas) on the vaporization behavior of the alloying elements.• Generation of different microstructure formations due to a follow up heat treatment.• Development of correlation matrices between processing, microstructure and properties for manufacturing of structures whose microstructure is optimized for the local amount of properties.Frank Walther, WPT (2nd applicant) • Characterization of microstructure and defect formation as a function of process parameters and the post processing as well as their impact on the quasistatic and fatigue deformation and fracture behavior.• Further development of the mechanism-based testing methodology on basis of instrumented load increase and constant amplitude tests for a resource-efficient characterization of the fatigue behavior at room and high temperatures.• Development of a physically-based model for description of the impact of microstructure and defect characteristics on the fatigue behavior at room and high temperatures.

• DFG Programme: Research Grants