Rajarshi Banerjee - US grants

TECHNICAL: The program focuses on a study of the early stages of second phase nucleation and phase separation in Ti alloys. The full exploitation of Ti alloys requires manipulation of microstructure to affect a range of combinations of properties, and this in turn requires a detailed understanding of the processes involved in the evolution of these microstructures. There are many significant unanswered questions concerning the evolution of microstructures in Ti alloys, especially regarding the early stages of second phase nucleation and phase separation. It is necessary to focus effort on developing a more thorough understanding of these processes, and this is a central objective of this project. This effort consists of five tasks, each bearing upon the stated aim of the project, namely to develop a detailed understanding of the nucleation of alpha-Ti in a beta-matrix including the influence of the omega phase and beta phase separation and the formation of colony and basketweave microstructures. The five tasks are: characterization of the precipitation of allotriomorphic alpha-Ti on prior beta grain boundaries, characterization of the formation of Widmanstatten plates from allotriomorphic alpha-Ti, characterization of early stages of formation of basketweave microstructure, determination of the influence of metastable phases, and, forming a unified view of nucleation and phase separation in Ti alloys. Research will involve the application of novel state-of-the-art characterization tools to the study of critical issues related to microstructural evolution in multiphase Ti alloys. Emphasis will be placed on determining the mechanisms underlying the early stages of second phase nucleation and phase separation in the beta matrix. In addition, the elemental partitioning between the different phases and compositional profiles at interphase boundaries in these alloys will be determined at the highest achievable accuracy. A concurrent theme will be to determine the accuracy, fidelity and interpretability of data and information obtained from the two different types of analytical procedures, namely scanning transmission electron microscopy-based electron energy loss spectroscopy and the 3D local electrode atom probe tomography. NON-TECHNICAL: These alloys have been applied in a number of product areas, including commercial aircraft and engines and, in contrast, bio-medical engineering, largely because of a combination of attractive properties and because they are of relatively low density. The research program is aimed at the provision of computation tools for the prediction of microstructure/property relationships in materials. The successful implementation of the 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 provision of research tools capable of prediction of properties in these alloys will have a marked impact on industry. The educational outreach programs will have a significant influence on encouraging high school students with diverse ethnic backgrounds to enter science and engineering disciplines. Due to its geographic location, the College of Engineering and the Department of Materials Science and Engineering at UNT, are in a unique position to offer such education and training to the workforce of the Dallas-Fort Worth metroplex.

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).

This award supports the renovation and modernization of approximately 2,900 square feet of space within the University of North Texas' (UNT) Center for Advanced Research and Technology (CART), located in the university's Discovery Park (about 4.5 miles north of the main campus). As part of CART, UNT will create a modern, model facility, called the UNT Nanofabrication Analysis and Research Facility (NARF), which is to be an open-access "one-stop-shop" for advanced device fabrication and analysis across multiple length and time scales. The renovations will consolidate currently spatially distributed, advanced characterization and analysis instruments; upgrade the space to include high speed cyber connectivity permitting remote access and control of these instruments; and integrate this space with a clean room and technology incubator.

Intellectual Merit: NARF will use "open system design" architecture to maximize collaboration and shared use of equipment, "integration for fabrication" to maximize entrepreneurial activities characterized by co-location of a clean room and technology incubator, and a "community/school-friendly" setting, where researchers share results and explain their work in real-time or via distance to visitors. The facility will host a unique trio of tools consisting of a dual-beam focused ion beam instrument, a high resolution transmission electron microscope, and a local electrode atom probe, capable of true atomic scale analysis of the structure and chemistry of materials, as well as many other advanced instruments, into direct proximity of one another. NARF will foster fundamental research involving nanoscale characterization and analysis applied to a wide variety of materials systems and devices, and will allow for the first time at UNT, true 3D characterization of the nanoscale structure and composition of specific components and failure sites in semiconductor devices, as well as interfaces in hybrid materials for aerospace, biomedical, and energy-related applications.

Broader Impacts: One of the primary impacts enabled by NARF will be the research training of graduate and undergraduate students, as well as post-docs and external researchers from industry, in the use of sophisticated characterization and analysis equipment. NARF will provide researchers a range of different equipment under one roof and allow them to appreciate the novel research possibilities afforded by these various techniques. Such an impact is not possible if the equipment is isolated and located at geographically scattered locations across the campus, as it is currently.

Abstract

TECHNICAL SUMMARY: The proposed effort consists of five tasks, each bearing upon the stated aim of the proposal, namely to develop a detailed understanding of the role of various structural instabilities on microstructural evolution in titanium alloys. The five tasks are: determination of the factors governing intra-granular nucleation of alpha in the beta matrix, precipitation of allotriomorphic alpha-titanium on prior beta grain boundaries and formation of alpha sideplates in titanium alloys, characterization of the formation of the basket-weave microstructure, characterization of the formation of refined laths of (secondary) alpha-titanium in ribs of beta-titanium, and a summarizing task involving the development of a unified mechanistic model of nucleation and phase separation in titanium alloys. The research will involve primarily the application of novel state-of-the-art characterization tools to study critical issues related to microstructural evolution in multi-phase titanium alloys. Emphasis will be placed on determining the mechanisms underlying the early stages of second phase nucleation. In addition, the elemental partitioning between the different phases and compositional profiles at interphase boundaries in these alloys will be determined at the highest achievable accuracy. A concurrent theme will be to determine the accuracy, fidelity and interpretability of data and information obtained from the two different types of analytical procedures, namely scanning transmission electron microscopy-based electron energy-loss spectroscopy and 3D local electrode atom probe tomography.

NON-TECHNICAL SUMMARY: The proposed program focuses on a study aimed at formulating a detailed understanding of the role of various structural and compositional instabilities on microstructural evolution in titanium alloys. These alloys have been applied in a number of product areas, including commercial aircraft jet engines and, in contrast, bio-medical engineering, largely because of a combination of attractive properties and because they are of relatively low density. The full exploitation of titanium alloys requires manipulation of their microstructures to affect a range of combinations of properties, and this in turn requires a detailed understanding of the processes involved in the evolution of these microstructures. There are many significant unanswered questions concerning the evolution of microstructures in titanium alloys, especially regarding the early stages of second phase nucleation. It is necessary to focus effort on developing a more thorough understanding of these processes, and this is a central objective of the present proposal. Recent significant increases in the level of sophistication of characterization tools present a real opportunity to make detailed observations of the early stages of microstructural evolution, and much of the work proposed here is based on the application of these new and improved techniques of materials characterization.

1134882 Colorado School of Mines; Michael Kaufman
1134873 University of North Texas; Peter Collins

The Center for Advanced Non-Ferrous Structural Alloys will focus on the physical metallurgy of non-ferrous alloys (alloying and processing effects on microstructure, properties and performance) and on the industries that develop, manufacture, and use these alloys. Colorado School of Mines (CSM) and the University of North Texas (UNT) are collaborating to establish the proposed center, with CSM as the lead institution.

The proposed Center aims to establish the industrial support, operational mechanisms, and a prospective research portfolio for a viable research Center that will conduct critical basic and applied physical metallurgy research of direct relevance to the industries that develop, manufacture and use advanced non-ferrous structural alloys. The PIs are proposing the following topical areas: high performance alloys (nickel base super alloys and titanium base alloys), lightweight alloys including aluminum, magnesium (and their composites), and advanced alloys and processes. The PIs will insure that students have the opportunity to work on state-of-the-art projects and to be mentored by both experimental and modeling experts. The management of these focus areas is being modeled after the highly successful Advanced Steel Products and Processing Center at CSM, namely, by having companies designate what portion of their membership fees they wish to have distributed into the three specific focus areas.

The proposed Center has the potential to improve sustainability and profitability of US manufacturing by developing advanced non-ferrous alloys that could reduce energy consumption and pollution in the manufacturing of these alloys. The research would also improve the competitiveness of US manufacturers. Given that the focus of the proposed center will be on the physical metallurgy of structural non-ferrous alloys, the associated programs of study at the two institutions will be reexamined and potentially modified in order to insure that the undergraduate and graduate curricula are consistent with this focus. In other words, both institutions will work to insure that the undergraduate and graduate students receive proper education and training in order for them to be well grounded in fundamental principles of physical metallurgy. As a center interacting with industry, the PIs intend to reach out to local communities to bring their attention to the issues facing this particular industry sector and how the institutions can assist these industries as they compete in these global markets. The center will also insure that diversity is one of the criteria in the selection of both undergraduate and graduate students who are considered for the industry relevant projects.

TECHNICAL SUMMARY:
The proposed program focuses on novel non-classical mechanisms of solid-state precipitation in metallic alloys, with a primary focus on titanium (Ti) alloys. The significance of the proposed program stems from the interrelationship between microstructure and properties in these alloys where these interrelationships have been determined experimentally. 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 depends critically on accurate descriptions of the nucleation process, so that the models may be as physically relevant as possible. Hence, it is the role of the proposed program to provide such accurate descriptions of the factors that influence the nucleation process. The specific non-classical mechanisms of precipitation in Ti alloys that will form the subject of the proposed research are, the refined distribution of the alpha phase in Ti precipitated from a matrix of the beta phase by the pseudo-spinodal mechanism and the coupled mixed-mode mechanism of omega precipitation, with concurrently occurring displacive and diffusional processes, in contrast to the legacy understanding. The formation of an even more refined distribution of alpha-Ti in a beta-matrix with the omega phase as a precursor will also be investigated. In the main, the research will involve the application of novel state-of-the-art characterization tools to the study of critical issues related to the two novel non-classical precipitation mechanisms. Emphasis will be placed on determining the mechanisms underlying the early stages of second phase nucleation. In addition, the elemental partitioning between the different phases and compositional profiles at interphase boundaries in these alloys will be determined at the highest achievable accuracy and precision. A concurrent theme will be to determine the accuracy, fidelity and interpretability of data and information obtained from the two different types of analytical procedures, namely scanning transmission electron microscopy-based electron energy loss spectroscopy and x-ray energy dispersive spectroscopy, and the local electrode atom probe tomography.

NON-TECHNICAL SUMMARY:
The proposed research program involves a focused effort aimed at formulating a detailed understanding of novel non-classical precipitation mechanisms in Ti alloys. The proposed research effort brings together state-of-the-art characterization tools for addressing these mechanisms associated with Ti alloys. While the focus of the proposed program is on titanium alloys, it should be noted that the mechanisms being investigated, especially non-classical precipitation mediated via compositional fluctuations of small amplitude, are applicable in general to other metallic materials, and, in principle, also to ceramic and semiconducting systems. Additionally, the program will also result in the development of useful new research tools for nanoscale characterization which will be applicable to a wide range of metallic materials beyond Ti alloys. The proposed research program is part of a larger effort aimed at the provision of computation tools for the prediction of microstructure evolution and microstructure/property relationships in materials, an integral part of the national efforts under the Materials Genome Initiative (MGI) and the Integrated Computational Materials Engineering (ICME) initiative. 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 provision of research tools capable of prediction of properties in these alloys will have a marked impact on industry. The educational outreach programs will have a significant influence on encouraging high school students with diverse ethnic backgrounds to enter science and engineering disciplines. To that end, a very successful outreach program has involved interactive demonstrations at the Columbus' Center of Science and Industry (COSI) where children and students of all ages experience the world of materials through scanning electron microscopes. Due to its geographic location, the College of Engineering and the Department of Materials Science and Engineering at UNT, are in a unique position to offer such education and training to the workforce of the Dallas-Fort Worth Metroplex.

Non-technical Summary
This DMREF research program aims to formulate an integrated computational materials science and engineering (ICMSE) approach and, consequently develop tools, to accelerate the development of new types of alloys that most likely will have been missed by the traditional trial-and-error method. This effort is an integral part of the national efforts under the Materials Genome Initiative (MGI) and the Integrated Computational Materials Engineering (ICME) initiative. The successful implementation of these new methodologies and design strategy for materials R&D will have a profound impact on industrial exploitation of new materials and optimization of existing ones. The provision of such ICMSE tools, applicable to an important class of widely applicable structural materials, will have a marked impact on a broad range of advanced technological areas including aerospace, transportation and energy. Because future materials R&D activities, requiring substantially reduced time and cost cycles, must integrate computational materials research with critical experiments, the proposed program will directly prepare graduate students to immediately contribute to the success of ICMSE in industry. Additionally, the proposed training programs for researchers involved in materials development will accelerate the implementation of the new methodology in industry, resulting in very much increased effectiveness of our materials technologists. Regarding educational outreach, the present DMREF program encourages high school students with diverse ethnic backgrounds to enter science and engineering disciplines.

Technical Summary
This research program involves the integration of sophisticated computational models, at multiple scales, highly advanced materials characterization techniques, and combinatorial and accelerated methods for materials processing and property evaluation. Such a unique coupling will undoubtedly raise significantly the state-of-the-art in the discovery and development of new structural materials. Regarding the targeted material system involved in the proposed program, i.e. titanium alloys, the focus is on the exploitation of recently discovered non-conventional transformation pathways. Thus, recent theoretical and experimental investigations suggest possibilities of achieving extremely fine and uniform alpha+beta microstructures exhibiting substantially improved properties through these non-conventional transformation pathways including pseudo-spinodal decomposition and precursory phase separation. Using an integrated computational materials science and engineering (ICMSE) approach, the development of next generation of Ti alloys based on these new and promising transformation mechanisms will be accelerated. For the first time, alloy development will be led by computational modeling, mechanistically informed and validated by critical experiments involving novel combinatorial methods for materials processing and state-of-the-art characterization techniques. The focus is on Ti alloys for structural applications in a broad range of advanced technological areas including aerospace, transportation and energy (petrochemical and nuclear). The outcomes will lead to a microstructure simulator, a property simulator, and an alloy design simulator for titanium alloys. An additional exciting aspect of this program is that the development and application of this new methodology is expected to result in new science in alloy design.

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.