December 3, 2003 FRONTIERS IN MATERIALS SCIENCE
VINSE COLLOQUIUM SERIES
Dr. Steven Nutt
Department of Materials Science
University of Southern California
"Bimodal Nanocrystalline Al-Mg Alloys for High Strength and Enhanced Toughness"
Abstract. Multi-scale (bimodal grain size) Al-7.5%Mg alloys were prepared by blending cryomilled nanocrystalline powder with unmilled coarse-grained powder in selected proportions, followed by consolidation. The resulting alloys showed dramatic increases in strength, while retaining acceptable ductility and toughness. The deliberate addition of unmilled powder produces a multi-scale microstructure. The matrix is nanostructured, containing grains 100-300 nm, while elongated coarse-grained bands result from extrusion. The balance of toughness, ductility, and strength can be controlled by the proportions of milled and unmilled powders. This process demonstrates a new approach to designing and producing bulk nanocrystalline metals that exhibit a combination of high strength and enhanced ductility and toughness. |
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