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MAX Phases: A Ripple in Time

Abstract:

Layered solids are ubiquitous in nature and man-made systems from geological formations and ice, to microelectromechanical devices and classical composites. MAX phases are a family of layered materials, namely ternary transition metal carbides and nitrides, that bridge the gap between metals and ceramics. One key mechanism recently identified in the deformation of MAX phases is atomistic buckling, termed ripplocations, which can lead to mesoscale nonlinear kink band formation (NKB). In contrast to dislocation motion, bulk ripplocations have no Burgers vector and no polarity, and when forming NKB’s provide a unique intrinsic toughening mechanism under load. At the same time, MAX phases catastrophically fail in a globally brittle manner due to the fact that critical resolved shear stresses have drastically reduced pathways for dislocation motion. As such, understanding the competition of ductile, pseudo-ductile and brittle deformation and failure mechanisms across stress states and strain rates is imperative to moving towards tailoring their layered anisotropy for specific strength or stiffness performance metrics in next-generation structures. This talk presents strain rate and orientation investigations under dynamic compression and fracture on MAX phases titanium silicon carbide (Ti3SiC2), and highly-oriented titanium aluminum carbide (Ti2AlC). Ripplocation nucleation, self-assembly and propagation to the point of permanent kink banding, which is fundamental to the deformation of all layered solids, as well as the potential benefits of highly-textured MAX phases will be discussed. All presented investigations will highlight current advances in full-field quantitative visualization techniques in extreme experimental mechanics.

Bio:

Leslie Lamberson is a currently an Associate Professor in Mechanical Engineering and Mechanics, with affiliated appointment in the Materials Science and Engineering Department at Drexel University. Dr. Lamberson received her B.S. in Aerospace Engineering from the University of Michigan, her M.S. in Aerospace Engineering at the Georgia Institute of Technology, and her Ph.D. in Aeronautics from the California Institute of Technology. Prior to her faculty appointment, she was a postdoctoral research scholar with K.T. Ramesh at Johns Hopkins University in the Extreme Materials Institute. Dr. Lamberson is a former Lockheed Martin Skunk Works Engineer, and a NASA Glenn faculty fellow in the Materials and Structures for Extreme Environments Division. She is a recipient of an ONR Young Investigator Award and an NSF CAREER award. Her expertise lies in dynamic experimental mechanics.

For additional information on the speaker: http://dynamic.mem.drexel.edu

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