Super Responses of Decomposed Two-Phase Nanodispersions to External Stimuli: Theory and Modeling

点击翻译按钮获取中文摘要

TECHNICAL SUMMARYThis award supports theoretical and computational investigations of new functionalities in materials with a focus on giant low hysteretic recoverable strain response to applied stress, magnetic and electric fields. This effect is expected in traditional precipitation hardened alloys when they are two-phase nanodispersions consisting of precipitates of a low-symmetry phase embedded in a cubic matrix. The precipitates of a low-symmetry phase formed at the early stages of decomposition are single domain particles that have one of several symmetry-related orientation variants. The strain response is caused by coherent switching between different orientation variants of the precipitates. This is a new effect. The switching- generated macroscopic strain is giant in comparison with the intrinsic responses to the applied fields. If the applied field is stress, the material becomes superelastic; if it is a magnetic field, the material becomes an extrinsic super-magnetostrictor. This project will investigate conditions that could lead to a giant low hysteretic strain response of precipitation hardened alloys to the applied fields. The scientific goal of the project is to develop a blueprint for the search of alloy systems and the processing conditions that would provide exceptional functional properties of these systems. The goal of this project is to provide access to a new class of functional materials with unique combinations of mechanical and functional properties. Specific goals of this project include: 1. Developing theories and computer models that can explicitly take into considerations all physically significant energy contributions affecting the recoverable stress and/or magnetic field-induced switching of single-domain orientation variants and thus macroscopic strain response. 2. Clarifying mechanisms that control the formation of coherent two-phase material systems with flexible orientation variants of nanoprecipitates. In particular, the development of the understanding of the effects of elastic moduli, lattice mismatch, and magneto-structural coupling of the constituent phases, as well as the optimization of the effects of thermo-mechanical/ thermo-magnetic treatments. 3. Establishing correlations between the microstructure and dynamic strain responses to differently directed applied stress and/or magnetic fields. This award also provides support that will enable: (1) further collaboration with experimentalists in order to validate our findings and search for advanced functional materials of this kind, (ii) the education and training of the next generation of materials researchers.NON- TECHNICAL SUMMARYThis award supports an exploration of the practically uncharted territory of the functional behavior of decomposed nanostructured materials. Nanodispersive decomposed systems are technologically important structural materials that have been a subject of intensive research for decades. However, there are very important aspects of these materials that have been previously overlooked: under certain conditions, the precipitation hardened nanodispersions can acquire unique functional properties. The materials can have giant recoverable strain responses to the external stimuli, which can be interpreted as superelasticity, super magnetostriction, shape memory and ferromagnetic memory effects. The goal of this theoretical and computational research is to: (i) investigate the formation of these kinds of materials during decomposition and ways to optimize their properties, (ii) study the mechanisms and dynamics of their switching-induced strain responses, and (iii) develop a blueprint for engineering a new class of spontaneously formed inexpensive functional materials with desired super responses to applied stress, electric, and magnetic fields. The project has the potential to open a practically untapped source of super-responsive functional materials. In particular, its success would open a way to develop materials with dramatically enhanced magneto-mechanical properties, and to engineer inexpensive magnetostrictive alloys that are free from critical rare-earth elements that are difficult to obtain, but still have desired properties comparable or even exceeding those of rare-earth based compounds.This award also supports educational activities to educate and train a postdoctoral research associate and graduate students, preparing them for the challenges of materials research in the 21st century which will require an interdisciplinary approach and synergy between different branches of physics and engineering.