MateriAlZ Seminar: Ankit Srivastava
Friday, October 28, 2022 - 10:50 a.m. MST
Ankit Srivastava
Associate Professor of Materials Science & Engineering
Texas A&M University.
"Slip, Cracking and Kinking in Atomically Layered Materials"
Harshbarger 332 | Zoom link, passcode: 10810
MateriAlZ Seminar website | YouTube | Twitter
Abstract
A family of atomically layered ternary carbides and nitrides with a combination of strong intralayer and weak interlayer atomic bonds, referred to as MAX phases, possess unique set of properties. These are lightweight, elastically stiff, thermodynamically stable and refractory, like ceramics, but are also thermal and electrical conductor, thermal shock resistant, damage-tolerant and readily machinable, like metals. Herein, Dr. Srivastava aims to better understand the single crystal level mechanical response of MAX phases to unravel the nature and origin of their unique set of properties, in particular, their damage-tolerance. To this end, he first characterize the mechanical response of single crystals of MAX phases using micropillar compression testing. Dr. Srivastava's results show that MAX phases depending on their crystallographic orientation, either undergo crystallographic slip, slip followed by cleavage cracking or cracking without any appreciable amount of slip. His results also show that the crystallographic slip in MAX phases does not follow Schmid’s law. These micropillar experiments are then complemented with crystal plasticity finite element analysis using a novel constitutive model that accounts for the non-Schmid effects on the crystallographic slip. Next, using an in-house designed and build fixture Dr. Srivastava carries out in situ SEM mechanical testing of carefully grown single crystals of these materials. The results of this exercise show that even though MAX phases readily crack along the weakly bonded crystallographic planes, onset of an abstruse mode of deformation, referred to as kinking in these materials, induces large crystallographic rotations and plastic deformation that physically heal the cleavage cracks. As a whole, these results provide new insight into the unusual damage tolerance of MAX phases.
Bio
Ankit Srivastava is currently an associate professor in the Department of Materials Science & Engineering at Texas A&M University. Prior to Texas A&M, he was a postdoc at Brown University from 2013-2015. He received his Ph.D. in materials science & engineering in 2013 together with MS degrees in physics and materials science & engineering from the University of North Texas. He also worked at the Bhabha Atomic Research Centre in India from 2007-2009. His research interests lie within mechanics of materials with a focus on understanding deformation and failure mechanisms of structural materials. He is a recipient of 2016 ACSPRF Doctoral New Investigator award, 2017 ASME-AMD Haythornthwaite Foundation Research Initiation Award, 2020 NSF CAREER award, 2022 and 2021 AISI finalist medals, and 2022 TMS-AIME Robert Lansing Hardy Awards.