CAREER: Understanding the Role of Nanoprecipitates in Advanced Metastable Titanium Alloys

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NON-TECHNICAL SUMMARYIn materials science, strength is the measure of a material’s ability to bear a load or carry weight without failing. Alternatively, ductility is a measure of a material’s ability to bend, stretch or spread without breaking into pieces. Often, increasing the strength of a material results in a decrease of ductility and vice versa. This project supports fundamental research focused on the design of Titanium alloys that overcome this typical strength-to-ductility trade-off by carefully tailoring the elemental make-up of said alloys. This careful tailoring controls how specific parts of the metal are arranged on an atomic level to have a certain chemical composition and arrangement that increases the material’s strength without reducing the material’s overall ability to bend or stretch. This type of design is known as metastability engineering. This project investigates how parts of Titanium alloys having the same elemental makeup and atomic structure change with both temperature and chemical composition and how they deform under various circumstances. To explore this behavior, real-time and “after the fact” studies are performed using cutting edge equipment to discover connections between local chemistry, different environments and very small particles in the metal that are nanometers in size and have only recently been discovered in Titanium. The fundamental knowledge established in this project advances the ability to design lightweight Titanium alloys with both high strength and high ductility. Metastable titanium alloys are desirable for aerospace, automobile, bio-medical and chemical industries, due to their high strength-to-weight ratio, ability to absorb impact, resistance to chemical deterioration and compatibility with biological applications. As an example, relative to just one of these industries, improvements to these alloys can help to increase aircraft fuel efficiency, reduce fuel consumption, lower carbon emissions and ultimately, benefit the environment. This project also develops education modules for students in a K-12 Summer Camp as well as lab experiences for undergraduate and graduate students at the University of Nevada Reno. Both sets of activities feature high powered microscopes providing students from local Reno communities exposure to science and technology while also providing opportunities for women and underrepresented minorities to learn materials science for the purpose of developing the future scientific workforce.TECHNICAL SUMMARYThis project aims to advance a novel alloy designing strategy known as metastability engineering, by studying microstructural evolution and deformation in metastable Titanium alloys. The project will identify the critical role of the recently discovered, orthorhombic nano-precipitate, O prime (O’) in the spatially confined phase transformations of Titanium and its alloys. Advanced ex-situ and in-situ characterization techniques are employed to explore three specific phenomena: (i) The relationship between alloy composition and O’ nano-precipitates; (ii) The role of O’ in refining precipitate microstructure; and (iii) the role of O’ in regulating martensitic transformations. Multiscale ex- and in-situ experimental characterization using scanning electron microscopy, transmission electron microscopy, scanning transmission electron microscopy and atom probe tomography are used. This research progresses the ability to realize metastable alloys of Titanium having both high strength and high ductility. Education modules and outreach activities focused on electron microscopy creatively engage students in K-12, undergraduate and graduate level study. The education modules and activities are enhanced by a remote-controlled transmission electron microscope and a portable desktop scanning electron microscope to capture a wide range of interests and expose all to meaningful science. These education activities provide students in the neighboring community unprecedented access to science in real-time and offers to the student body at the University of Nevada, Reno a practical means of enhancing their in-class instruction with exposure to advanced characterization being performed at their institution. All activities assist with developing a future STEM workforce by generating interest in materials science to students at all ages.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.