MECHANICAL ENGINEERING & MATERIALS SCIENCE
Jörg M.K. Wiezorek, PhD
538i Benedum Hall | 3700 O’Hara Street | Pittsburgh, PA 15261
Professor
P: 412-624-0122 wiezorek@pitt.edu
Professor Wiezorek’s research expertise and interest center on the study of processing-structureproperty relationships in advanced materials systems. Transmission electron microscopy (TEM) based imaging, quantitative diffraction and analytical spectroscopic methods, and other modern micro-characterization techniques feature prominently in his research. Combining the principles and practice of physical metallurgy and metal physics with electron microscopy observation and measurements with appropriate computer simulations, the research leads to the discovery of novel materials and materials behaviors, explanations of the mechanical, magnetic and other physical properties of modern materials, with an emphasis on intermetallic and metallic systems. Current research thrusts include: (1) Determination of the electron density of transition metals and intermetallics by quantitative electron diffraction and DFT; (2) Surface modification for enhanced performance of structural materials for harsh environments; (3) Ultrafast (nano-scale spatio-temporal resolution) in-situ TEM of pulsed laser induced transformations (e.g. rapid solidification) in metals and alloys; (4) Innovative manufacturing processes for the sustainable preparation of high performance permanent magnet materials.
Unique New Capabilities – Quantitative TEM Orientation imaging microscopy (OIM) enables effective quantification of microstructural metrics (e.g. grain size, texture, grain boundary character) for polycrystalline materials and is popularly implemented with SEM instruments. Using precession electron diffraction (PED) patterns obtained with 2nm spatial resolution a new TEM-OIM method facilitates automated phase mapping, grain size and texture determination at length scales not accessible by SEM-OIM, permitting study of many previously inaccessible problems in nanoscaled crystalline materials. Texture and grain scale evolution in pulsed laser processed nano-sale metal and alloy thin films (e.g. Figure top) and the origin of the extraordinary strengthening in severe plastic deformation processed steels were determined successfully by TEM-OIM [McKewon et al. (2014) Acta Mat. 65, p56; Idell et al 2013) Scripta Mat. 68, p667]. Validation of density functional theory (DFT) calculated materials properties is often hampered by lack of suitable experimental data for the material of interest. Comparisons of the electronic charge density distribution obtained from quantitative convergent beam electron diffraction (CBED) can provide a new experimental metric for rapid DFT validation protocols. Our CBED method for simultaneous measurements of Debye-Waller factors and structure factors is broadly applicable to crystalline materials. It has been used to determine the nature of bonding (e.g. metallic ‘bonds’ visualized in magenta between blue-green electron charge depleted atoms in FePd, Figure bottom) in transition metals (e.g. Cr, Fe, Ni, Cu) and intermetallics (e.g. NiAl, TiAl, FePd, Ni2MnGa). Comparison with DFT calculated results indicate need for improved theoretical treatments [Sang et al. (2013) J. Chem. Phys 138, 084504].
Research Themes and Expertise • Processing-Structure-Properties in Advanced Metals & Alloys
• Property measurements (mechanical, magnetic, thermal/calorimetric).
• Physical Metallurgy & metal physics
• Processing of metals and alloys by… e.g. Conventional & Severe Plastic Deformation (e.g. ECAP), Heat treatments (T≤1200˚C, in air-, controlled atmosphere, vacuum), Melting & Solidification, Laser Irradiation (surface melting, annealing, shocking, sintering), Physical Vapor Deposition (E-beam evaporation, pulsed-laser deposition, sputtering).
• Electron Microscopy/Diffraction/Spectroscopy by SEM & TEM/STEM, structure & composition (HREM, EDS/EELS, CBED, PED OIM, EBSD OIM, in-situ TEM). • X-ray diffraction (phase ID & fractions, texture, stress/strain, crystallite size). DEPARTMENT OF MECHANICAL ENGINEERING AND MATERIALS SCIENCE
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