CBE & MSE Seminar: How Do Crystals Slip?

Jian-Min Zuo
Friday, April 5, 2019 - 3:00 p.m. to Saturday, April 6, 2019 - 3:55 p.m.
McDonnell Douglas Engineering Auditorium (MDEA)
Jian-Min Zuo

Professor
Dept. of Materials Science and Engineering
Seitz Materials Research Laboratory
University of Illinois, Urbana-Champaign, IL

Abstract: How do crystals slip? This is a fundamental question in crystal plasticity that has long puzzled physicists and materials scientists alike. The early experimental work of Elam, Taylor and others in the 1920s established convincingly that single crystals of metals under stress develop large slips along certain crystallographic directions. By the 1930s, the role of dislocations in crystal deformation was already established. The observation by transmission electron microscopy in the 1950s furthered the study of dislocations, their characters, microstructure and their interactions that formed a foundation of modern materials science. However, relating microscopic dislocation motion to mesoscopic mechanic properties remains extremely challenging.

IndentersHere, we report our exploration of the dislocation slip mechanism and alloy strengthening enabled by advances in electron microscopy. We focus on multiprincipal-element alloysor high-entropy alloys (HEA). Starting from the structure of alloys, we show how aberration corrected STEM and electron diffraction enable characterization of lattice distortion at atomic- to mesoscopic scales. Next, we show the measurement of a broad range of dislocation motions from nm/s to m/s in compressed nanopillars of an HEA, Al0.1CoCrFeNi. Putting these results together, we will identify the dislocation interaction mechanism for large crystal slips, and provide critical insights into the deformation of high-entropy alloys.

Bio: Jian-Min Zuo is the Ivan Racheff Professor in the Department of Materials Science and Engineering at the University of Illinois, and a fellow of the American Physical Society and the Microscopy Society of America. He is a specialist in electron diffraction and characterization of materials. His research portfolio at University of Illinois includes the study of structure and property relationships in metals, semiconductors and nanostructures; and the development of electron microscopy techniques. His current research interests include the structure and dislocation dynamics in high-entropy alloys, energy storage materials, in-situ electron microscopy and ultrafast transmission electron microscopy.

 

Host: Prof. Xiaoqing Pan