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Michael J. MillsTaine MacDougal ProfessorPh. D., Stanford University, 1985 Tel. (614) 292-7514 Office: 478 Watts Hall
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Mills' Research Group sites: |
Professor Mills received his B.S. degree in Materials Engineering from San Jose State University in 1980, and M.S. and Ph.D. degrees in Materials Science and Engineering from Stanford University in 1985. After two years as a research associate at the Ecole Polytechnique Federale in Lausanne, Switzerland, Dr. Mills joined Sandia National Laboratories as a senior member of the technical staff. In the fall of 1994, Dr. Mills joined the faculty of the Department of Materials Science and Engineering as Associate Professor, and was promoted to Professor in the fall of 2000. In Autumn 2004, Dr. Mills was named the Taine G. McDougal Professor of Engineering by the OSU College of Engineering.
His primary research interests are the relationship between microstructure and properties of materials, with special emphasis on transmission electron microscopy techniques which make it possible to the study the structure and chemistry of materials down to atomic dimensions. Through a detailed analysis and characterization of crystalline defects such as dislocations and grain boundaries, Prof. Mills and his group are developing improved, fundamental insights into the mechanical behavior of several important metallurgical systems. His present research programs include studies of creep and deformation in commercial titanium alloys, strengthening mechanisms in aluminum alloys and dislocation processes in nickel-based superalloys. He has authored over 80 peer reviewed journal articles and made numerous invited presentations of his group's research. Dr. Mills organized Symposium S on "Integrative and Interdisciplinary Aspects of Intermetallic Compounds" for the Fall 2004 meeting Materials Research Society.
Development of Improved Aluminum Alloys
Mechanisms of Strengthening and Corrosion in 5000-Series Alloys Pechiney Rolled Products/CAMM
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This project involves investigation of strengthening mechanisms and improvement of properties in various aluminum alloys, including 5000 and 7000 series. Plastic instabilities which limit the formability of aluminum alloys has been studied, and correlated with the effect of composition, temperature and strain rate. Extensive TEM characterization of precipitation in 5000 and 7000 series alloys is being used to address both strengthening and critical corrosion issues in these alloys.
Order and Precipitate Stengthening in Al-Mg-Cu Alloys Alcan/CAMM
Subtle microstructural changes occur during aging of 2000 series alloys. We are using high resolution TEM techniques to characterize these atomic-scale processes, such as the local ordering seen here in this Al-Mg-Cu alloy.
Deformation Mechanisms in Intermetallics and Superalloys
Modeling the Creep Performance of TiAl Alloys National Science Foundation
Two phase TiAl alloys based on the gamma (L10 structure) and alpha2 (DO19 structure) phases are presently being developed for a variety of high temperature structural applications. Creep strength is one of the critical characterisitics which will potentially limit the application of TiAl alloys. This program is aimed at understanding the effect of microstructural scale, lamellar orientation and composition on creep in equiaxed and fully lamellar TiAl-based alloys. Based on this knowledge, we are developing microstructure-based, predictive models of creep deformation for this important class of alloys.
Deformation Mechanisms in Superalloys and Aluminides Department of Energy-Office of Basic Energy Sciences
In this program the mechancial properties of single crystals of intermetallic compounds within the (Fe,Ni)-Al pseudobinary system, as well as two-phase gamma/gamma' Ni-based superalloys, are being studied and correlated with detailed TEM investigation of dislocation structures developed during deformation. In ordered intermetallic compounds, the dislocation structures can be far more complex than in disordered alloy systems, as evidenced in this high resolution TEM image of a dislocation core in the gamma' phase of CMSX-6. These detailed observations are being coupled with atomisitc simulations of core structure and dynamics, thereby providing a fundamental understanding of the complex dislocation processes which control the deformation behavior in these materials.
Deformation Processes in Titanium Alloys
Mechanistic Modelling and Mitigation of Primary Creep in Titanium Alloys Air Force Office of Scientific Research
Primary creep is the dominant mode of deformation for titanium alloys at lower temperatures under most service conditions. In this program, we are performing detailed studies of the mechanisms and microstructural elements which contribute to low temperature primary creep in single phase alpha and two-phase alpha/beta titanium alloys. We have found that simple heat treaments can be used to signifcantly alter the primary creep transients through manipulation of short-range ordering which causes planar lip in the alpha-phase of most commercial titanium alloys.
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Dwell Fatigue of Ti-6242 Federal Aviation Administration
Ti6242 is a common alloy used in critical rotating components of commercial jet engines. The insertion of dwell times at maximum load causes a significant reduction in the fatigue life of this alloy. The primary objective of program is to produce micro-tensile and micro-fatigue samples of Ti-6242 whereby the constitutive behavior of the individual microstructural elements of the material can be characterized independently. This information is then used to inform microstructure-based finite element codes under development by Prof. Somnath Ghosh and his group in Mechanical Engineering at OSU.
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