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

技术概述：本研究项目的目标是确定在纳米尺寸的金属中获得高强度和高延展性组合的基本标准。这些标准将通过使用纳米压头以不同的速率进行受控机械变形实验来阐明。随后，将通过显微镜工具检查缩进区域。实验利用了主成分相的稳定性随着晶粒度的减小而增加。所调查的标准确定了金属材料的主要组成相的稳定性是否对管理高强度金属材料的延展性负责。变形行为的变化将作为从纳米颗粒区域到传统微米区域的颗粒尺寸的函数来研究。基于晶粒度和主成分相稳定性之间的关系，将开发出对多种材料系统具有预测能力的物理模型。非技术总结：这项研究的结果将扩大加工具有优异成形性能的高强度、高塑性合金的最新水平。对高强高塑性组合变形机理的理解，对于指导未来强韧金属材料的发展具有重要意义。最终目标是确定指导方针，以开拓材料的新前沿，用于涉及能量吸收和成型性的轻型和高效解决方案。此外，将开发新的技术来了解材料的行为，这将适用于其他金属系统。根据该计划，研究生和本科生都将接受金属研究方面的培训。高中生将通过暑期项目从事科学和技术工作。

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.