Bonding, Structure, Defects and Diffusion in ‘Tough’ IronBased Bulk Amorphous Alloy

Friday, September 26, 2008 3:00 – 4:00 pm
Room 610, M&M Building

Prof. Gary J. Shiflet
Department of Materials Science and Engineering, University of Virginia

Abstract

Can brittle bulk metallic glasses be further designed to exhibit fracture toughness?And, can this be done without loss of other superior properties, such as, strength(currently 4 GPa)? Yes to both questions. Bulk amorphous metals are quitecommon today and nearly every major metal alloy system can be synthesized intoa bulk glassy material (Fe-, Cu-, Ni- Ti-, Zr-, Mg-based, etc., but not Al). To beuseful, the task now is to make them damage tolerant. This talk will emphasize ourstrategy for increasing alloy plasticity through bonding studies and current effortsto understand defects and structure in amorphous iron-metalloid alloys.  Thedesign of amorphous steel with high glass formability has provided the base alloycomposition used to further improve overall plastic behavior by reducing its highshear modulus. Our systematic investigation highlights the role of interatomicinteractions, in addition to the individual alloying elements, in determining theelastic moduli or Poisson’s ratio, and hence the ductility. For instance, as asolution to alloy brittleness for amorphous steel, ab initio quantum chemistrymethods and EELS indicate that phosphorous improves plasticity because of theunusual bonding associated with electron transfer from phosphorous to iron.Extensions to other alloy systems will also be discussed to test this fundamental approach.

Biography

Dr. Shiflet is currently the WG Reynolds Professor at the University of Virginia where he has been afaculty member in the School of Engineering since 1980. He has a BS and MS in physics and PhD in metallurgicalengineering (1981), all from MTU. Shiflet’s primary interests are in solid-state phase transformations of metal alloysand concerns thermodynamics, nucleation and the kinetics associated with growth of new phases. He haspublished more than 250 papers and holds several patents concerning various amorphous metal alloys. Dr. Shiflethas been awarded two creativity awards from the National Science Foundation, the ASM Research Award (SilverMetal) and has been elected as a Fellow of the American Society for Materials and Japan Advancement of Scienceand was selected as Scientific American 50 for 2004. He is a member of The Metallurgical Society of AIME and theAmerican Society for Materials.


Comments Closed