The Interplay Between Grain Size and Austenite Stability on Constitutive Deformation Behavior of High Strength-High Ductility Combination Nanostructured Materials

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TECHNICAL SUMMARY:The objective of this research project is to determine the fundamental criteria for obtaining a combination of high strength and high ductility in metals with grain sizes in the nanometer range. These criteria will be elucidated by conducting controlled mechanical deformation experiments at different rates using a nanoindenter. Subsequently, the indented region will be examined via microscopy tools. Experiments utilize the increasing the stability of the principal constituent phase with decreasing in grain size. The criteria investigated define if the stability of the principal constituent phase of the metallic material is responsible for governing the ductility of high-strength metallic materials. Changes in deformation behavior will be studied as a function of grain size from the nanograin regime through the conventional micrometer regime. Physical models with predictive capabilities for a wide range of material systems based on the relationship between grain size and stability of the principal constituent phase will be developed.NON-TECHNICAL SUMMARY:The results of this research will extend the state-of-art for processing of high-strength, high-ductility alloys with superior formabilities. The understanding of deformation mechanisms underlying combined high strength and high ductility is expected to be important in guiding the development of future strong and ductile metallic materials. The ultimate objective is to determine guidelines to pioneer a new frontier of materials for light and efficient solutions involving energy absorption and formability. Furthermore, new techniques will be developed to understand material behavior that will be applicable to other metallic systems. Both graduate and undergraduate students will be trained in metals research under this program. High-school students will be engaged in science and technology through summer programs.