Jorg M. K. Wiezorek - US grants

0094213
Wiezorek

This CAREER award is aimed at a quantitative, mechanism-based description of the processing-microstructure-property relationships and annealing behavior in reversibly ordering metallic systems. Model alloys based on the ferromagnetic L10- and L12-ordered intermetallic phases in the Fe-Pd system undergoing severe plastic deformation (SPD) processing will be the focus of the research. The main experimentation techniques are differential scanning calorimetry (DSC), vibrating-scanning-magnetometers, mechanical testing, and in-situ and post-mortem microstructural observations by transmission electron microscopy and x-ray diffraction. Strategies for property optimization and microstructural control will be devised based on the mechanistic models of the processes responsible for the observed microstructural changes. Unique exploitation of reaction processing of heavily deformed reversibly ordering alloys will be used to control microstructures at the nanoscale. The educational component centers on the development of Web-based educational tools and their implementation into upper-level MS&E undergraduate and graduate courses. These new tools will incorporate results and experimental capabilities developed from the research and they will be made available to the public cost-free. The national and international collaborations that will be fostered through this award offer unique opportunities for interaction with outstanding researchers in the field of intermetallics and physical metallurgy of advanced materials.
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This research facilitates a systematic study of scale-related effects in truly bulk nanostructured functional intermetallic alloys with commercial potential. There is considerable interest in these functional intermetallics for advanced permanent magnet technologies, e.g. thin film media, data storage and futuristic micro-devices. Refinement of the microstructure to the nanoscale offers enormous potential for property improvements. Future success of these and many other intermetallics requires a detailed knowledge of the synergistic interplay between competing solid-state reactions during processing.
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0140317
Mao
Nanoscale multilayers, composed of sub-micrometer thick layers of two or more species of materials are of significant interest for high-technology applications and devices in many fields of industry, including microelectronics, magnetic recording, optics, and micro-electro-mechanical systems. The physical performance and reliability of these devices depend on the structural integrity of the multilayers. Hence, there is considerable worldwide research interest in the mechanical response of multilayers, including the deformation and fracture behavior. The development of viable novel devices based on these advanced multilayer systems and their further improvement requires a basic understanding of the fundamental processes that are the agents of the macroscopic deformation and fracture performance.

The main goal of the proposed project is the investigation of the processes of micro-plasticity involved in the fracture of carefully selected model nanoscale multilayer systems by dynamic in-situ straining TEM experiments as well as static post-mortem TEM. This research will produce new insights regarding dislocation mobilities and interactions with interfaces and their relationship to crack growth in multilayers. Hence, the fundamental relationships between processes of plasticity, local flow and fracture in Cu/Ni, Cu/Cr and Cu/TiN multilayers with selected interfacial structure and layer thickness will be elucidated. The project objectives are:

to investigate the deformation and fracture process of metal/metal (Cu/Ni, Cu/Cr) and metal/ceramic (Cu/TiN) multilayers by in-situ straining transmission electron microscopy.

to predict the fracture resistance and the effect of interfaces on crack tip stresses in the nanolayers as a function of layer thickness, and crystal orientation using a dislocation-interface interaction model.

Both in-situ TEM fracture experiments and dislocation based modeling of the deformation and fracture processes in the nanolayers will be performed. Two graduate students (one in materials science and one in mechanical engineering) will be trained during the project as the follows:

Student 1: in-situ TEM experiment on microplasticity and fracture in nanolayers (Dr. Wizorek)
Student 2: dislocation based modelling on the deformation and fracture process (Dr. Mao).

Dr. Mao will be responsible for the design of the in-situ straining experiments and dislocation-based modeling. Dr. Wiezorek will be responsible for the performance of TEM characterization and in-situ TEM testing. Because of the comprehensive and interdisciplinary nature of the proposed research, the involvement of students in the project will provide effective means for training of the new generation of materials scientists for the new century.

TECHNICAL SUMMARY: This project is an investigation of rapid solidification processes in pure metal and Al-rich Al(Cu) thin films. The main technique is in-situ transmission electron microscopy (TEM) using the dynamic TEM (DTEM) at Lawrence Livermore National Laboratory (LLNL) for ultrafast electron diffraction (UED) and imaging. There are no other measurement techniques currently capable of observing rapid solidification processes with interfacial velocities ranging from about 0.1 to 100 m/s in metal thin films with the required nano-scale spatial and temporal resolution offered by the DTEM. The research will reveal quantitative dynamic details of the extremely rapid liquid-solid transformation and other transient phenomena (e.g. solid-solid transitions) associated with Al and Al-rich Al(Cu) thin films and other FCC, BCC and HCP metals after single-shot pulsed laser melting. Robust modeling software codes, validated by direct comparison with quantitative measurements from in-situ DTEM experiments on pure metals, will be developed for the pulsed-laser melting. Post-mortem and in-situ microstructural characterization will be used to investigate microstructural evolution and defect formation in the solid state following solidification of pure metals with different crystal structures. The study of Al-rich Al(Cu) thin films is expected to help identify the conditions of morphological destabilization of the growth interface as function of pulsed laser power, alloy composition and heat-extraction parameters for hypo-eutectic, eutectic and hypereutectic compositions between Al and Al2Cu. The data obtained on parameters that determine the stability or instability of the transformation front will enable validation of theoretical solidification models. Apart from delivering basic scientific knowledge on metals under the extreme conditions of laser-induced rapid solidification, state-of-the-art experimental techniques for in-situ TEM will be developed for the purpose of probing the behavior of material volumes at time scales close to those accessible by computational modeling.

NON-TECHNICAL SUMMARY: Solidification is a ubiquitous and fundamental process in materials fabrication, especially for metals, which are critical to energy generation and transmission, transportation and information technologies. Under extreme conditions of laser processing the growth dynamics determine the final microstructure and consequently performance-related properties in engineered components and devices. Understanding such phenomena is scientifically interesting and technologically important. The results of this research will be disseminated by peer-reviewed publications and presentations. The project involves outreach to high school students, via the Pennsylvania Junior Academy of Science and the development of semester-long research experiences for students enrolled in the new Pittsburgh Science & Technology Academy (grades 6-12). Students will receive training in vacuum and laser science, physical metallurgy, thin film science, micro-fabrication methods, scattering and diffraction physics, transmission and scanning electron microscopy, crystallography, thermodynamics, transport phenomena and numerical methods for materials modeling. Visits to, and continuous interaction with, LLNL will provide professional preparation outside the academic environment and access to state-of-the-art instrumentation.

1337731
Yang
Technical Abstract
This Major Research Instrumentation Award supports the acquisition of an environmental transmission electron microscope (ETEM), a high-resolution electron microscope with a simplified differential pumping system that permits gas introduction directly into the column. As a conventional TEM the instrument will enhance the current electron microscopy capabilities in teaching, user training and research. The capability to visualize structural changes at the sub-nanoscale level under operational environmental conditions will bring essential insights to many materials issues, such as the effect of dopants and impurities on processing and corrosion, defect (dislocation, grain boundaries and interface) migrations, thermally induced phase transformations, heterogeneous catalyses, nano-scale functional materials, and the environmental stability of materials in general. The low accelerating voltage minimizes damage of oxide species and soft materials, thereby providing the ability to visualize the dynamics of polymers, tissue engineering, drug delivery, biomaterials and biomineralization. This will be the first ETEM in the greater Western Pennsylvania area. It will be housed at the University of Pittsburgh in the Swanson School of Engineering (SSoE) and will be a part of the Nanofabrication and Characterization Facility (NFCF) in the Peterson Institute of NanoScience and Engineering (PINSE). It will be linked to the electron microscopy facility in the Structural Biology department, School of Medicine. The NFCF is a user facility available to all national and international researchers. The broad visibility and access to this instrument will contribute to nano- and meso-scale science and technology, biology, energy and sustainability research and to the training of post-docs, graduate students and undergraduate students. This instrument will also be used in teaching courses in Electron Microscopy, Nano-characterization, Thin Films, Biomaterials, Nanomaterials and Nanotechnology. As a part of PINSE, it will contribute to the education of high school students and under-represented groups, especially African-American, as part of the NSF-Nanotechnology Undergraduate Education (NUE) outreach program and Pitt Engineering Career Access Program (PECAP) program, respectively.
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This award from the Major Instrumentation program will support the installation of the first Environmental Transmission Electron Microscope (ETEM) in the greater Western Pennsylvania area. The instrument will be housed at the University of Pittsburgh in the Swanson School of Engineering (SSoE) as part of the Nanofabrication and Characterization Facility (NFCF), a user facility available to all national and international researchers. TEM is a powerful tool to visualize materials at the nanoscale and below. ETEM enables unique insights on the dynamic processing/structure/property relationships of nanomaterials with impact in a broad spectrum of science and engineering areas, such as oxidation, corrosion, catalysis, nano-processing, bio-mineralization, tissue engineering and drug delivery. The broad visibility and access to this instrument will contribute to nano- and meso-scale science and technology, biology, energy and sustainability research and education of post-docs, graduate students and undergraduate students. This instrumentation will also be used in teaching Electron Microscopy, Nano-characterization, Thin Films, Biomaterials, Nanomaterials and Nanotechnology courses. It will contribute to the education of high school students and under-represented groups, especially African-American, as part of the NSF-Nanotechnology Undergraduate Education outreach program and Pitt Engineering Career Access Program, respectively.

This Grant Opportunity for Academic Liaison with Industry (GOALI) award supports fundamental research on an innovative manufacturing process for the improved preparation of high performance permanent magnet materials. The process combines the preparation of high-purity micro-particulates that are internally composed of an ultrafine-grained structure from MnAl base alloys using a novel machining-based process. During subsequent low-temperature thermo-mechanical consolidation a composition-invariant solid-state phase transformation will be used to obtain dense bulk ferromagnetic aggregates. Magnetic and mechanical properties will be measured. Microstructure evolution during thermo-mechanical processing will be determined by x-ray diffraction and electron microscopy measurements. Physics based numerical models will be combined with experiments to determine the process-structure-property relationships. The research will provide the science underpinning the creation of the internally nanostructured alloy particulates, as well as for the phase transformation facilitated retention of the nano-scale grain size in the low-temperatue consolidated ferromagnetic aggregates.

The research provides new processing and materials science knowledge to meet the critical need for the effective manufacture of rare-earth-metal-free magnetic materials, which are critical to technologies used in the conversion between mechanical work and electrical power, as well as in transmission and distribution of power. Improved manufacture of permanent magnet materials based on abundant ingredients supports the implementation of clean wind power and electric vehicle technologies. Additionally, the underlying process schema is amenable for adaptation to a range of alloy systems. Therefore, the processing science knowledge the research will deliver is expected to advance the field of powder-particulate based manufacturing of functional and structural material in general. The research project involves an interdisciplinary academia-industry team from the University of Pittsburgh and Alcoa, provides synergy for project resources, ensures the industry relevance of the research, enables multifaceted graduate education for students, and expedites technology commercialization. It will also positively impact engineering education, promote lifelong learning for industrial practitioners, and broaden participation of underrepresented groups in research.

Non-Technical Abstract

This activity develops scientific understanding of the formation of microstructures in multi-component metallic materials during solidification under far-from-equilibrium conditions. Binary and ternary model alloys will be studied using unique electron microscopy in conjunction with characterization of the microstructures. Direct correlation of local features in the solidification microstructure with the conditions of their formation will deliver experimental data sets unobtainable with other approaches that are suitable for validation of predictions from competing theoretical models of alloy rapid solidification. The research enhances scientific understanding of microstructure formation during solidification in complex alloys and contributes to the development of techniques for nano-scale resolved studies of materials. Understanding of microstructure formation during processing of engineering materials is a fundamental challenge of the field of materials science and engineering (MSE). It enables identification of strategies for property tailoring for optimal material performance in a technological application. Solidification is ubiquitous in fabrication of metallic materials, which are particularly critical to energy generation and transmission, advanced transportation, biomedical and information technologies. Research results will be emanated by journal publication and presentations at conferences. Integration with instructional resources and outreach module development will enhance the MSE undergraduate curriculum. Modules for targeted outreach will be developed collaboratively with student teams and sustain improved MSE outreach efforts at the University of Pittsburgh. Future members of the US science, technology, engineering and mathematics workforce will receive research training, advanced science and engineering education, leadership and mentoring opportunity. Collaboration with the Lawrence Livermore National Laboratory team provides synergy for project resources and multi-faceted professional preparation outside of academia. The activity will positively impact engineering education, promote lifelong learning, broaden participation of underrepresented groups in research and advance the scientific knowledge of transformations in metallic alloys under technologically relevant non-equilibrium conditions.

Technical Abstract

Solidification is a ubiquitous and fundamental process in materials fabrication. Under extreme conditions arising in rapid solidification processing the migration of solid/liquid interfaces is driven far-away from equilibrium and kinetic factors can become dominant over thermodynamic factors in determining the final microstructure. We use the movie-mode dynamic transmission electron microscope (MM-DTEM) for nano-scale spatio-temporal resolution in situ imaging observations and diffraction measurements of rapid solidification transformations in alloy thin films. Complementing the in situ studies with quantitative post-mortem micro-characterization delivers direct correlation of local features in the solidification microstructure with the conditions of their formation during the irreversible transformation under-far-from-equilibrium rapid solidification. Focusing on concentrated binary Al-Cu and Al-Ag alloys, and for ternary Al-Cu-Ag alloys the research will deliver accurate global and locally resolved information on the transformation interface, including average and local velocity, changes in these velocities, and the morphology associated with changes in crystal growth modes. Post-mortem analyses of solidification microstructures provide compositional gradients, crystal structures, as well as the local arrangements, size, shape and composition of the constituent phases, which may differ from those that would form at or near equilibrium conditions. The use of thin film alloy specimens enables study of rapid solidification transformation microstructure formation for unexplored regimes of composition (e.g. hypereutectics in Al-Cu) and very large transformation rate, suitable to elucidate details of transitions to banded morphology and partitionless alloy crystal growth for instance. Effects of atomic size misfit, faceting tendencies, chemical ordering and interfacial coherency, as well as Ag addition effects on two-phase solidification microstructure formation will be determined using Al-Cu and Al-Ag alloys Al-Cu-Ag ternaries. The proposed research will deliver unique experimental data sets and insights suitable to evaluate current rapid solidification models and will enhance scientific understanding of microstructure formation in solidification of multi-phase alloy systems.