Event
MSE Seminar - Dr. David Williams, Lehigh University
Friday, April 27, 2007
1:00 p.m.
Room 2108, Chemical and Nuclear Engineering Bldg.
Annette Mateus
301 405 5207
amateus@umd.edu
"Towards a Fundamental Understanding of Grain Boundaries in Metals and Alloys"
Dr. David Williams
Department of Materials Science and Engineering
Lehigh University
Bethlehem, PA 18015
Grain boundaries play a major role in determining the properties of almost all engineering materials. Very often the boundary is the source of brittle or premature failure and, therefore, its characteristics limit the performance of the material. In particular, intergranular failure is a widespread fracture mode including such undesirable phenomena as hydrogen embrittlement, temper embrittlement and liquid-metal embrittlement. A common factor in such failures is the presence of elements that segregate to the grain boundary. To understand grain-boundary chemistry and its role in intergranular failure, we need to be able to characterize the boundaries in detail.
Characterization can take many forms but, for a full comprehension of the problem, it is necessary to understand the crystallographic structure, the elemental chemistry and the local bonding at the boundary, often down to the nanometer level or below. The Transmission electron microscope (TEM) is unique in its ability to determine all these characteristics in a single instrument (using diverse techniques such as imaging, diffraction, X-ray and electron spectrometry) thus permitting correlation of the structure, chemistry and properties of grain boundaries. This talk will describe the application of these various TEM techniques to grain-boundary segregation in a range of metals and alloys, including prospects for improved analysis via the latest generation of aberration-corrected analytical TEMs.
BIOGRAPHY
David B. Williams is the Harold Chambers Senior Professor of Materials Science and Engineering at Lehigh University. He obtained his BA (1970), MA (1974) PhD (1974) and ScD (2000) from Cambridge University. From 1974-1976 he was a Science Research Council Fellow at the Department of Metallurgy and Materials Science in Cambridge. In 1976 he moved to Lehigh as an Assistant Professor, becoming Associate Professor in 1979 and Professor in 1983. He directed the Electron Optical Laboratory at Lehigh from 1980 to 1998, chaired the Department of Materials Science and Engineering from 1992-2000 and was Vice Provost for Research from 2000-2006. He has co-authored and edited 11 textbooks and conference proceedings, and has published 220 journal papers and 200 abstracts/conference proceedings in the general areas of analytical TEM and the application of these techniques to studies of precipitation and segregation. He has given 270 invited presentations at universities, conferences and research laboratories in 28 countries. He is a Fellow of TMS, ASM International and the Royal Microscopical Society (UK), Editor of Acta Materialia and Past President of the International Union of Microbeam Analysis Societies.
