Dr. Jan Schroers, Robert Higgin Professor of Mechanical Engineering and Materials Science at Yale University will give a seminar titled "Local Deformation Mapping in Alloys" to the interested faculty and students at Discovery Park.

Abstract

Microstructures possess multiscale features (~10-10 m – 10-3 m) comprised of a vast number of atoms. To date, they cannot be directly reconstructed by the characteristics of their constituents. Therefore, a general quantitative understanding of microstructure-property-relationships remains elusive. To address this challenge, we propose local deformation mapping (LDM) as a mechanical characterization technique. LDM is capable of probing microstructures with a resolution of ~10 nm2 over macroscopic dimensions of cm2, generating ~1012 simultaneous data points. This is realized by pressing an array of nanopores against the microstructure, which creates local stress gradients that force the microstructure into the pores. The diffusing or slipping material from the microstructure fills the nanomolds’ pores to form an array of nanorods on top of the microstructure. The nanorod array represents the microstructure’s local plastic response which is spatially separated from the underlying microstructure. This separation enables sensitive kinetic and chemical characterization of this response. Collectively, these nanorods constitute a set of ~1012 measurements forming the deformation response map generated in a single step. We present analytical models to transform this nanorod-based deformation map to material characteristics map. These characteristics, such as diffusivity, and dislocation density and velocity, which contribute to the overall mechanical response of the microstructure, are mapped as a function of the local microstructural features with high-resolution. We focus here primarily on creating local diffusivity maps related to the high homologous temperature deformations. As particular examples, we show one-step determination of grain boundary diffusivity as a function of misorientation angle for a polycrystalline microstructure and mapping of phase boundaries. First usage of LDM has revealed an unknown fast diffusion mechanism in alloys with eutectic phase boundaries. LDM fills the need for higher local resolution carried out over length scales exceeding those of microstructures to gain deeper and more holistic insights into the deformation of microstructures.

Bio

Jan Schroers is the Robert Higgin Professor of Mechanical Engineering and Materials Science at Yale University. He received his Ph.D. in 1997 from RWTH Aachen, Germany, and was a postdoctoral fellow at Caltech prior to joining Yale. He has been a Visiting Professor at EPFL Lausanne in Switzerland (2013-2014) and MIT (2016-2017). He is a Scientific Advisor at Supercool Metals (2013-present) and Desktop Metals (2016-present). He was the IRG leader of Yale’s NSF-MRSEC during 2011-2017. His research interests include Metallic Glasses, Combinatorial Material Science, and Multiscale Manufacturing.