Most structural materials are used as metallic alloys, often multi elemental. This is the case for certain steels or titanium alloys for which the alloying elements are rare and/or available in low concentrations in the Earth crust and sometimes difficult to refine. Indeed, the number of elements that humans can use is merely around one hundred. Moreover, that number is further limited due to scarcity or toxicity. There is a pressing need to open a path to the future with scientific technology, which makes possible to effectively utilize limited elements. This can perhaps be used to create materials for renewable societal infrastructure in severe resource conditions. In this context, structural materials are required to have superior mechanical characteristics while reducing the requirement for rare earth elements. In the framework of the present proposal, owing to the versatility of powder metallurgy (PM) routes, namely spark plasma sintering (SPS) and hot isostatic pressing (HIP), a new concept that combines severe plastic deformation (by high energy milling) and PM routes (SPS and HIP) will be used to develop and design harmonic microstructures. The harmonic structure will have a 3D network structure of continuously connected "shell" with ultrafine grains and a dispersive structure of coarse-grained "core". This makes them special and different compared to heterogeneous “nano-micro” bimodal microstructure usually produced via various metallurgical routes. The targeted materials are Ti-based: pure titanium (Ti), Ti-6-4 (Ti6Al4V) and ß-Ti (Ti-15-3-3 (Ti15V3Cr3Sn3Al) alloys (medical implants, aeronautic applications…). After processing by means of process encompassing PM routes (SPS and HIP) a combination of characterization techniques at both macroscopic (from quasi-static to impact loadings) and mesoscopic/microscopic (X-Ray Diffraction (XRD), in-situ XRD tensile tests and electron microscopy techniques) levels will be carried out to capture the elementary details of the deformation mechanisms and to provide the necessary input parameters into the predictive models for such complex harmonic structures. Indeed, numerical simulations and mechanical modeling will be proposed and will deal with damage nucleation and crack propagation that might result from deformation incompatibility between the fine-grained shell and the coarse-grained core. The models may help to capture the critical parameters and feedback the elaboration to improve the microstructure design. In addition to the full understanding and prediction of the macroscopic mechanical behavior, we intend to answer the following questions by the end of the project: • Are developed materials with harmonic microstructures more efficient in terms of mechanical properties than the same materials with conventional and/or bimodal microstructures? • Are pure Ti harmonic microstructures better than the Ti-6-4 or T-15-3-3 conventional alloys? • Will the expected high strength and high ductility properties allow making practical applications of structures that are light, compact and have superior reliability possible? • … If so, then we can save not only the rare and difficult to refine alloying elements but also costly thermo-mechanical treatments and machining used to transform them. This will contribute at some level to: • Resources and energy savings, • CO2 reduction, • Recyclability, • Uncovering new applications to provide society with the fruit of research results and contribute to the welfare of mankind. The knowledge resulting from this project will be likely to participate in the recent initiatives taken at national level for a renewal of metallurgy, from the point of view of fundamental research, technology transfer as well as the training of young scientists of all levels.