Advanced Characterization Techniques for Quantifying and Modeling Deformation: Session IV
Sponsored by: TMS Extraction and Processing Division, TMS Structural Materials Division, TMS: Advanced Characterization, Testing, and Simulation Committee, TMS: Materials Characterization Committee
Program Organizers: Arul Kumar Mariyappan, Los Alamos National Laboratory; Irene Beyerlein, University of California, Santa Barbara; Wolfgang Pantleon, Technical University of Denmark; C. Tasan, Massachusetts Institute of Technology; Olivia Jackson, Sandia National Laboratories
Tuesday 2:30 PM
March 21, 2023
Room: Aqua 311A
Location: Hilton
Session Chair: Yifan Zhang, Purdue University; Donald Brown, Los Alamos National Laboratory
2:30 PM Invited
Coupled Neutron Diffraction and Modeling Study of the Formation and Recovery of Dislocations in Elemental Tantalum and Ferritic HT-9 Steel: Donald Brown1; Reeju Pokharel1; Aaron Kohnert1; Laurent Capolungo1; Levente Balogh1; Bjorn Clausen1; Tarik Saleh1; 1Los Alamos National Laboratory
Microstructure-aware models are necessary to extrapolate mechanical properties of materials to environmental conditions which are not easily reproduced in the laboratory, e.g. nuclear reactor environments. Elemental tantalum provides a relatively simple BCC system in which to develop a microstructural understanding of deformation processes which will then be applied to a much more complicated BCC steel alloy, HT-9. The evolution of texture, lattice strain and dislocation density in each material was monitored through deformation and subsequent annealing with in-situ neutron diffraction measurements. The observed data will be used to develop both polycrystalline plasticity models and Discrete Dislocation Dynamics (DDD) models. The observed and calculated evolution of the microstructural features will be critically compared.
3:00 PM
Coded Apertures for Fast Depth Resolved Diffraction and In-situ Characterization: Dina Sheyfer1; Doga Gursoy1; Jon Tischler1; Wenjun Liu1; Michael Wojcek1; 1Argonne National Laboratory
We develop a rapid data acquisition and reconstruction method to image the internal structure of crystalline materials using non-destructive X-ray Laue diffraction microscopy. Our method relies on scanning a coded-aperture across the diffracted beams, and a decoding algorithm to extract Laue patterns as a function of depth along the incident illumination path. This method provides rapid access to full diffraction information at sub-micrometer volume elements in bulk materials and thus can resolve locally in 3D crystal structure, its orientation and strain and can be utilized together with in-situ measurements. Here we present the underlying theory and demonstrate the utility of this approach with micrometre-resolution depth resolving measurements of grain orientations and sizes in polycrystalline Nickel foil.
3:20 PM
Monitoring Defect Structure Evolution in Titanium Alloys using High-Energy X-ray Diffraction: Kenneth Peterson1; Joel Bernier2; Jacob Ruff3; Darren Pagan1; 1Pennsylvania State University; 2Lawrence Livermore National Laboratory; 3Cornell High Energy Synchrotron Source
Cold dwell fatigue in titanium alloys is understood to consist of deformation localization, load transfer, and then failure at adjacent hard and soft grain pairings. However, it is currently difficult to predict precise locations of failure nucleation due to the interplay of deformation mechanisms, local loading conditions, and microstructural heterogeneity across length scales. Fortunately, the recent development of wide-dynamic range X-ray detectors now enable probing of 3D sample volumes to observe deformation across length scales and examine factors that contribute to cold dwell fatigue in situ, such as defect ordering and reconfiguration. In this study, high-dynamic range diffraction data collected from Ti-6Al-4V undergoing uniaxial tension and tension-only cyclic fatigue is analyzed using multiscale scattering and plasticity modeling to simultaneously characterize the evolution of defect structure ordering and intergranular interactions.
3:40 PM
Resolving Intragranular Stress Fields in Plastically Deformed Titanium Using Point-focused High-energy Diffraction Microscopy: Wenxi Li1; Hemant Sharma2; Kenesei Peter2; Sidharth Ravi3; Huseyin Sehitoglu3; Ashley Bucsek1; 1University of Michigan; 2Argonne National Laboratory; 3University of Illinois at Urbana-Champaign
The response of a polycrystalline material to a mechanical load depends not only on the response of each individual grain, but also on the interaction with its neighbors. These interactions lead to local, intragranular stress concentrations that often dictate the initiation of plastic deformation. Yet very few experimental studies have quantified intragranular stresses across bulk, three-dimensional volumes. In this work, a synchrotron X-ray diffraction technique called point-focused high-energy diffraction (pf-HEDM) is used to characterize intragranular deformation across a bulk, deformed, polycrystalline commercially pure titanium specimen. The results reveal the heterogenous stress distributions within individual grains and across grain boundaries. A stress concentration between a low and high Schmid factor grain pair and a stress gradient near an extension twinning boundary are observed. This work demonstrates the potential for understanding the local deformation associated with networks of grains and for informing mesoscale modeling in the future.
4:00 PM Break
4:20 PM
Understanding Variant Selections during Phase Transformation and Deformation Twinning in BCC Metals: Avinash Dongare1; Aadhithyan Kannan1; Ke Ma1; Avanish Mishra1; 1University of Connecticut
The deformation response of BCC metals can have contributions from dislocation slip, deformation twinning, and phase transformation. While recent capabilities can use in situ diffraction studies to identify the fingerprints of these deformation modes, the interpretation of the plasticity contributions to the deformation response is challenging as this is limited to post-mortem characterization of unloaded microstructures. Molecular dynamics (MD) simulations can successfully capture various deformation modes in metals and complement experiments using simulated diffractograms at various stages of evolution. A newly developed ‘virtual texture’ (VirTex) analysis is able to characterize phase/twin variants in deformed microstructures and virtual diffraction simulations can identify their contributions to peak shifts and broadening behavior. This talk will highlight our efforts to understand the role of new capabilities to characterize the role of microstructure and stress states on phase/twin variant selections during the deformation of BCC metals (Fe, Ta) and during unloading.
4:40 PM
Using Deep Learning to Reconstruct Grains from Simulated Far-Field Diffraction Data: Ashley Lenau1; Yuefeng Jin2; Ashley Bucsek2; Stephen Niezgoda1; 1Ohio State University; 2University of Michigan
Far-Field High Energy Diffraction Microscopy (ff-HEDM) is invaluable for quantifying the orientation and elastic strain within the bulk of a 3D polycrystalline sample. However, it has limited ability to capture morphology or orientation and strain gradients that is needed to model the mechanical behavior of metal materials. In this presentation, we demonstrate a deep learning framework that reconstructs the 3D grain shape given diffraction spots from a single grain. The network is based on Pix2Vox, which uses an encoder-decoder structure to convert multiple 2D images of an object into a 3D volume render. Unlike standard Pix2Vox, which uses a single encode-decoder for all 2D images, our network utilizes an independent encoder for each diffraction spot. The ground truth grain shapes are generated via DREAM.3D and the simulated ff-HEDM data is generated by a virtual diffractometer. While still in the nascent stages of development, here we demonstrate high-fidelity 3D grain reconstruction.
5:00 PM
3D Grain Interactions after Fatigue Loading in an Al-Li Binary Alloy via High Resolution X-ray Characterization Techniques: Sven Gustafson1; Wolfgang Ludwig2; Katherine Shanks3; Raquel Rodriguez-Lamas4; Can Yildirim4; Carsten Detlefs4; Michael Sangid1; 1Purdue University; 2University Lyon I; 3Cornell High Energy Synchrotron Source; 4European Synchrotron Radiation Facility
During cyclic loading, dislocations accumulate at microstructural features, such as grain boundaries, and will influence the surrounding microstructure; such structures of dislocations lead to intragranular variations of elastic strain and orientation. Historically, these intragranular variations have been difficult to probe experimentally without conducting measurements using destructive techniques, such as electron backscatter diffraction, and many such techniques are unable to measure elastic strain directly. In this study, high energy X-ray diffraction microscopy was conducted during high cycle fatigue loading of an Al-Li binary alloy. Individual grains were then probed by dark field X-ray microscopy to characterize their intragranular elastic strain and orientation. By spatially linking this intragranular characterization to the 3D specimen grain map and grain averaged elastic strains during loading, this study is able to provide insight into the effect neighboring grains have upon stress/strain localization at grain boundaries and its subsequent effect upon the fatigue performance of the material.