Events Calendar

Aerospace and Mechanical Engineering Department Seminar

Speaker: Katharine M. Flores , Professor and Associate Chair,Department of Mechanical Engineering and Materials Science

Talk Title: From the Atoms Up: Design and Deformation of Metallic Glasses and their Composites

Abstract:

Metallic glasses, metallic alloys with disordered atomic structures, have matured from laboratory curiosities to engineering alloys of interest for their remarkable mechanical properties and processability. The unique atomic structure of these alloys presents a number of challenges for describing and controlling their behavior, as well as intriguing manufacturing opportunities. Lacking long-range structural order and the attendant microstructure, metallic glasses do not require multiscale modeling to capture many essential characteristics of their behavior and thus are an ideal model system for the development of a computationally driven "atoms-up" approach to alloy design. We use molecular dynamics to determine the liquid fragility for a series of Cu-Zr alloys and discuss this measure of the dynamics of the system in light of observations of the short-range atomic ordering of the alloy. Based solely on these parameters calculated from molecular dynamics, we suggest an a priori predictor for glass forming ability.

While monolithic metallic glasses exhibit near theoretical strengths and large elastic deflections, their lack of extensive tensile ductility limits their structural applications. Microstructural control has long been the materials scientist's chief tool for improving material properties. By creating metallic glass-crystalline composites, we introduce microstructural features and gain control over the initiation and distribution of plastic deformation. Building upon our computationally-driven approach to the design of the glassy phase, we next seek to design metallic glass composites with desirable properties. This requires adequate understanding of the role of microstructure on the plastic deformation mechanisms in order to calibrate and validate the model. One family of composites utilizes ductile crystalline dendrites which precipitate from the melt prior to vitrification of the matrix. Our work to quantitatively characterize this microstructure and its role in the resulting mechanical behavior will be discussed. Full field strain mapping measured from in situ digital image correlation reveals that at relatively low strains, the glassy matrix acts as an isotropic "buffer layer" between crystals of different orientations, permitting the crystals to deform unimpeded along their preferred slip system.


Biography: Katharine Flores is Professor and Associate Chair of Mechanical Engineering and Materials Science at Washington University, as well as the Associate Director for the new interdisciplinary Institute of Materials Science and Engineering. After receiving her B.S. in Mechanical Engineering from Washington University in 1995, she attended Stanford University where she received her Ph.D. in Materials Science and Engineering in 2000. She joined the Materials Science and Engineering Department at the Ohio State University as an assistant professor in 2002, and moved to her current position at Washington University in July, 2012. Her primary research interest is the mechanical behavior of structural materials, with particular emphasis on understanding structure-processing-property relationships in bulk metallic glasses and their composites, an area in which she has worked for almost 15 years. She leads research projects on topics ranging from investigations of the structural origins of plastic deformation in metallic glasses to the design of new glasses with desirable properties and the development of new manufacturing techniques suited to the unique processing capabilities of these alloys, in an effort to accelerate their incorporation in mainstream and high performance applications. In 2005, she received two prestigious early-career awards for her work in this area, a National Science Foundation CAREER Award and an Office of Naval Research Young Investigator Award. In addition to her research, Dr. Flores is actively involved in outreach and was the Director of Education and Outreach for the Center for Emergent Materials, the NSF Materials Research Science and Engineering Center at OSU, from 2008-2012. In 2011, she was a co-recipient of an Ohio Faculty Innovator Award for her efforts to improve undergraduate instruction in materials science and engineering.

Host: Profs. Hodge/Eliasson

More Info: http://ame-www.usc.edu/seminars/9-26-12-flores.shtml

Location: Seaver Science Library (SSL) - Room 150

Audiences: Everyone Is Invited

Contact: April Mundy

Event Link: http://ame-www.usc.edu/seminars/9-26-12-flores.shtml