Polycrystalline Diffraction - A Primer for the 2016 APS NX School

Polycrystalline Diffraction - A Primer for the 2016 APS NX School Matthew P. Miller 1,2 1 Sibley School Of Mechanical and Aerospace Engineering, Cornell University 2 Cornell High Energy Synchrotron Source August 3, 2016 Overview This document is a compilation of notes from MAE 7110 Micromechanical Modeling and Diffrac- tion Experiments for Crystalline Solids a course in Mechanical and Aerospace Engineering at Cornell University taught by Darren Pagan and Matt Miller during the spring semester 2015. The focus of MAE 7110 is the use of a new class of synchrotron-based High Energy X-ray Diffrac- tion (HEXD) experiments that have evolved over the past decade at CHESS, APS Sector 1, the ESRF and other light sources around the world (cf. [1]). These experiments take advantage of the penetration power of high energy x-rays, in situ loading / heating environments and high speed area detectors to literally “watch” individual crystals within a polycrystalline aggregate deform during loading. These data are especially useful when used together with multiscale material modeling formulations [2]. The notes are a mixture of x-ray science, materials engineering and solid mechanics designed to train graduate students in the use of HEXD data to understand the deformation-induced distributions of stress and orientation in a deforming aggregate. In par- ticular, the use of the HEXD data in conjunction with material behavior models is emphasized. The course is biased towards engineers who need to develop an understanding of reciprocal space and diffraction and are mainly interested in the grain scale elastic-plastic deformation behavior of metallic polycrystals. After a primer on indicial notation, vectors and tensors, a general description of crystallography and diffraction is presented. The details of modeling a diffraction experiment from a continuum mechanics perspective is presented followed by a description of crystal-scale mechanics from the perspective of diffraction. Some references are included. The notes are definitely not a “how to” do these experiments. They are designed to complement the lectures in MAE7110 but between the notes the references and the resources at a place like CHESS/Insitμ (http://insitu.chess.cornell.edu/index.html) or the APS sector 1, someone interested in conducting these experiments can get started. There are no doubt inconsistencies and mistakes throughout - please let us know ([email protected]) when you find one/many. Good luck! 1

Polycrystalline Diffraction - A Primer for the 2016 APS NX School

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