High-conductivity and simultaneously high-strength materials are needed for the creation of winding wires for large high-field magnetic systems. Severe plastic deformation is used to prepare Copper-based high strength nanocomposites with a large number of continuous parallel Niobium filaments whose diameters are few tens of nanometers.
The resulting nanocomposite has an ultimate tensile strength of 2 GPa at 77K. In-situ tests are performed under synchrotron radiation on the nanocomposite wires containing Nb nanofilaments to study the evolution of elastic strains and peak profiles versus the applied stress. The elasto-plastic transition is also studied in the different phases with respect to microstructure size. Finally, a new criterion for the determination of the macro-yield stress is developed to determine the transition from elasto-microplastic to macroplastic regimes.
Lunch and refreshments will be served before the talk. Please join us!
New martensitic steel grades for improved thermal power plant efficiency
Dr. Peter Mayr Assistant professor of Materials Science and Welding
Graz University of Technology, Austria
Visiting Scientist to MIT on a Max Kade Fellowship, 9/09—9/10
Tuesday, November 10, 2009
4:00-5:00pm
Room 4-153
Seminar Abstract:
Increasing efficiencies of fossil-fueled thermal power plants requires significant increases of steam temperature and pressure, challenging the long-term stability and strength of steels. Within this talk, the state-of-the-art of alloy development for high temperature components is presented and the successful application of a holistic research concept to the development of a new 9Cr-3W-3Co,V,Nb,B,N steel is shown.
The alloy design is supported by thermodynamic and kinetic models. Microstructural evolution is predicted during the entire lifecycle, including production, processing and service, and coupled to actual material strength. Simulation results are validated using long-term creep and oxidation testing at service conditions, with microstructural evolution being studied by advanced analytical microscopy, in-situ high-temperature confocal laser microscopy and in-situ X-ray diffraction using synchrotron radiation.
This seminar is open to the entire MIT community. Contact Michael Demkowicz for more information: demkowicz@mit.edu.
Bridge Macro- and Micro- Scales in Describing Some Mechanical Properties of Solid Materials
Dr. Wen Jiang
Thursday, October 29, 2009
Room 13-2137
12:00 – 1:15 PM
Abstract: Macro-scale differential equation models have achieved great successes in solid mechanics; however, as the increase of computational power, micro-scale simulations have become more and more popular in discovering new phenomena of micro-sized solids. In the mean time, we need to bridge different scale models to further investigate physical mechanisms and conduct multi-scale analysis of atomic systems. I shall present some of our work in bridging continuum and atomic level analysis of some mechanical tests of solid materials. First we studied the indentation of an anisotropic layer by a rigid circular cylinder. Analytical results obtained from continuum modeling of the indentation were applied to identify three elastic constants of a cubic material (e.g., an FCC single crystal) and cracks in composites. Second we conducted several molecular mechanics simulations with the embedded atom method to study mechanical properties of gold. Information obtained from atomistic simulations was bridged with continuum level concepts and were used to understand the mechanisms of some physical phenomena, e.g., buckling and yielding of nanowires.
Wen Jiang received her MS in Civil Engineering from Zhejiang University, China in 2003 and her PhD in Engineering Science and Mechanics from Virginia Tech in 2008. Now she is a postdoctoral research associate in the Department of Mechanical, Aerospace and Biomedical Engineering in the University of Tennessee. Her research interests are in computational solid mechanics, nanomechanics and biophysics.
Sponsored by Assistant Professor Michael J. Demkowicz
Department of Materials Science and Engineering
Please join the Materials Research Society (MRS) and DMSE in its second Lunch and Lecture of the Fall semester with Professor Michael Demkowicz.
Pizza and refreshments will be served!
Tailoring nanocomposite properties by atomic-scale design of interfaces
Michael J. Demkowicz, John C. Chipman Assistant Professor of Materials Science and Engineering
Thursday, October 22nd
12:00pm-1:00pm (pizza and refreshments will be served at 11:40am)
The Chipman Room (6-104)
Abstract:
As the characteristic microstructural dimensions of a composite material decrease, its interface area-to-total volume ratio increases. In nanocomposites, interfaces make up such a large fraction of the total material that they may dominate its thermal, mechanical, and diffusion behavior. Understanding the atomic-level structure and properties of interfaces is therefore essential to explaining and controlling the macroscale behaviors of nanocomposites. This talk will present how atomistic simulations can shed light on the role of interfaces in the radiation response of Cu-Nb multilayer nanocomposites as well as how this insight can be used to design new radiation-resistant materials.
*The MRS “Lunch N Lecture” is a series of informal talks from any faculty member whose research interests are in materials. To learn more about the MRS and its lecture series, please visit the MRS homepage. Want to see a particular faculty member give a talk? E-mail the MRS officers at mrschapter.officers@mit.edu and give us suggestions!
