Collaborative Research: Fine Scale Alpha Precipitation and Resulting Deformation Mechanisms in Titanium Alloys

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Non-technical Summary:The broad goal of this experimental program is to develop a fundamental understanding of the structure of lightweight titanium (Ti) alloys, at different length scales, and its influence on the mechanical properties of these lightweight alloys. Such understanding will directly impact the ability to engineer the formation of nanometer scale precipitates (particles) within these Ti alloys, leading to substantially higher strengths. The proposed research effort brings together state-of-the-art characterization tools for addressing these precipitation mechanisms. While the focus of the proposed program is on titanium alloys, it should be noted that the mechanisms being investigated are applicable in general to other metallic materials, and, in principle, also to other types of materials, such as ceramics. Additionally, the program will also illustrate the advantage of using state-of-the-art tools in a correlative manner for nanoscale characterization which will be applicable to a wide range of metallic materials beyond Ti alloys. The successful implementation of the proposed research will result in new science and have a significant impact on industrial exploitation of materials and hence will make a positive contribution to the Nation's economy. The accurate mechanistic understandings developed will be used to inform computational tools, improving their accuracy, and this will have a marked impact on industry. The educational outreach will consist of multiple components, including the development of simple yet attractive modules, based on scanning electron microscopy, for high school and undergraduate students as well as the general public to the fascinating world of metals and materials in general. Such activities will have a significant influence on encouraging high school students with diverse ethnic backgrounds to enter science and engineering disciplines. These educational activities will closely couple with the educational and outreach activities of the Center for the Accelerated Maturation of Materials at Ohio State University. Due to its geographic location, the College of Engineering and the Department of Materials Science and Engineering at University of North Texas are in a unique position to offer such education and training to the workforce of the Dallas-Fort Worth Metroplex. In addition, the university has a substantial segment of students of Hispanic origin. These students will gain substantially from the research and education activities associated with this program.Technical Summary:This research program involves a focused effort aimed at formulating a detailed understanding of the factors influencing refined alpha precipitation in titanium (Ti) alloys, and its consequent impact on deformation mechanisms and mechanical properties. More specifically, this program focuses on the influence of metastable precursors, involving structural and compositional variations within the parent matrix, on solid-state precipitation of fine scale alpha in Ti alloys and its consequent influence on deformation mechanisms. The significance of this program stems from the interrelationship between the complex, often hierarchical (multiple length scales) microstructure, and properties in these (as in other) alloys. In the main, these interrelationships have been determined experimentally, and to reduce the time and costs of materials development and optimization, in the future these quantities will be the subject of prediction by computational models. The successful development of such computational models of microstructural evolution and deformation depends critically on accurate descriptions of the nucleation process, so that the models may be as physically relevant as possible. Furthermore, it is now well recognized that classical nucleation theories, based purely on statistical considerations, are in many cases inadequate descriptions for developing robust computational models. Hence, it is the role of this program to provide such accurate mechanistic descriptions of both intrinsic and extrinsic (e.g., metastable instabilities in the beta phase) factors that influence the nucleation process. Under this program these mechanisms will be derived solely from critical experiments. Additionally, the critical deformation mechanisms and resulting mechanical properties corresponding to such refined scale alpha distributions within the beta matrix of Ti alloys will be investigated under this program.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.