Seeing is Believing -- Understanding Environmental Degradation and Mechanical Response Using Advanced Characterization Techniques: An SMD Symposium in Honor of Ian M. Robertson: On-Demand Oral Presentations
Sponsored by: TMS Extraction and Processing Division, TMS Materials Processing and Manufacturing Division, TMS Structural Materials Division, TMS: Chemistry and Physics of Materials Committee, TMS: Corrosion and Environmental Effects Committee, TMS: Mechanical Behavior of Materials Committee, TMS: Nuclear Materials Committee
Program Organizers: Kaila Bertsch, Lawrence Livermore National Laboratory; Khalid Hattar, University of Tennessee Knoxville; Josh Kacher, Georgia Institute of Technology; Bai Cui, University of Nebraska Lincoln; Benjamin Eftink, Los Alamos National Laboratory; Stephen House, University of Pittsburgh; May Martin, National Institute Of Standards And Technology; Kelly Nygren, Cornell University; Blythe Clark, Sandia National Laboratories; Shuai Wang, Southern University of Science and Technology

Monday 8:00 AM
March 14, 2022
Room: Characterization
Location: On-Demand Room


Crack-tip Shielding by Dislocations Analyzed by HVEM and Its Effect on Fracture Toughness and Hydrogen Embrittlement: Kenji Higashida1; Masaki Tanaka1; 1Kyushu University
     Crack-tip dislocations and their shielding effect on fracture toughness is one of the most essential issues in the study of toughening mechanism of crystalline materials. In this work, detailed characterization of crack-tip dislocations was carried out by using high voltage electron microscopy (HVEM), and their shielding effect on fracture toughness was investigated by using photoelasticity and stress analyses for crack-dislocation interactions. In addition to this study, hydrogen effect on fracture toughness is discussed from the view point of dislocation shielding. It is well known that hydrogen embrittlement (HE) is quite different from low temperature embrittlement, since HE occurs in spite that hydrogen does not necessarily suppress plastic deformation or conversely enhances localized plasticity. In this presentation, a possibility of hydrogen effect on the dislocation shielding is discussed as the mechanism behind HE phenomena.

In Situ TEM with Ion Irradiation at the IVEM-Tandem: Past, Present and Future: Meimei Li1; Mark Kirk1; Wei-Ying Chen1; Pete Baldo1; Richard Sisson1; 1Argonne National Laboratory
    The IVEM-Tandem Facility consists of an intermediate voltage electron microscope (IVEM) interfaced to a 2 MV tandem ion accelerator and a 650 KV ion implanter. It provides a unique capability for real-time imaging of defects introduced in situ by ion beam irradiation/implantation. It has been used for a wide range of in situ TEM studies of defect dynamics to understand the fundamental mechanisms of defect formation, agglomeration, annihilation, and interactions. The recent addition of a low-energy ion source allows simultaneous low-energy helium implantation and high-energy heavy ion irradiation, to study the interaction of helium effect and cascade displacement damage. The current effort is to apply machine learning/artificial intelligence for computer vision-assisted, automated analysis of in situ video data to achieve real-time defect imaging and real-time defect analysis, and active learning for real-time predictions to assist on-the-fly decision making to guide subsequent experiments.

Quantitative 3-D Imaging of Damage Evolution in High-temperature Composite Materials, at Temperature under Load, Using In Situ X-ray Computed Micro-tomography with Digital Volume Correlation: Dong Liu1; Paul Forna Kreutzer1; Jon Ell2; Robert Ritchie2; 1University of Bristol; 2University of California, Berkeley
    High-temperature composite materials are becoming increasingly important for applications under extreme conditions. For instance, nuclear-grade graphite has been used as neutron moderator in gas-cooled nuclear reactors and projected for use in next-generation high-temperature designs. Moreover, textile ceramic composites represent the enabling materials for several major ultrahigh-temperature structural applications, in advanced gas-turbine engines, leading edges and contact surfaces for future hypersonic flight vehicles, and as accident tolerant fuel cladding in nuclear fission reactors. As such, life-prediction and damage assessment for their complex architectures presents a formidable challenge as measuring mechanical data and characterizing damage at such temperatures is so difficult. Here we describe the quantitative in-situ evaluation of tensile and fracture toughness properties in a range of materials from nuclear graphite, ceramic-matrix composites and nuclear fuel particles at temperatures above 1000°C, with real-time 3-D damage assessment using synchrotron x-ray micro-tomography and digital volume correlation analysis.

Some Challenges in Length and Time Scaling for Modeling Dislocations and Interface Reactions: David McDowell1; 1Georgia Institute of Technology
    We consider multiple crystalline plasticity model constructs that address evolution of dislocation and of dislocation-obstacle or –interface interactions over a broad range of length and time scales, from atomistic modeling and coarse-graining strategies through discrete dislocation theory to fields of nanoscale obstacles. The predictive character of each construct is considered, along with the notion of uncertainty of modeling phenomena at various scales and its role in combining atomistic modeling and experimental information to inform mesoscopic models. The role of dislocation substructure is considered. Gaps and future challenges are summarized.

Ian Robertson’s Impact on Materials Science: John Vetrano1; 1US Department of Energy
    Over the 40 years that Ian Robertson has been active in research, his research innovations and findings have produced an enormous impact in the field of materials science. His work on hydrogen embrittlement, radiation effects and in-situ deformation in the Transmission Electron Microscope set the stage for a broad swath of research built upon his findings. This talk will trace his impacts on the field of materials science in general, and both mechanical behavior and radiation effects in particular.

Sluggish Diffusion in Concentrated Solid-solution Alloys: Seeing is Believing: Yanwen Zhang1; 1Oak Ridge National Laboratory
    Controlling atomic motion to suppress defect evolution is a challenge in materials science. Sluggish diffusion is defined as reduced defect mobility or as decreased migration length of point defects or defect clusters. MD simulations have revealed enhanced sluggish diffusion in chemically disordered concentrated solid-solution alloys (CSAs) where the motion of interstitial defect clusters can be tailored from a long-range 1D motion in pure Ni to a short-range 3D mode in NiFe. Experimental observations have shown slow loop growth, delayed He bubble superlattice formation, and enhanced swelling resistance in complex CSAs. There is, however, a missing link between the atomistic simulations and observable defect features. Seeing is believing: work done by I. M. Robertson’s group provides direct observations of decreased dislocation loop glide distances and jump frequencies (i.e., enhanced sluggish diffusion) in Ni, CSAs and high-entropy alloys with increasing chemical complexity, bridges the knowledge gap and addresses the challenges.

Creep and Fracture Characterization in the TEM Using Full-field Measurement Methods and Finite Element Analyses: Yiguang Zhang1; Shen Dillon2; John Lambros1; 1University of Illinois Urbana Champaign; 2University of California, Irvine
    In-situ full-field displacement measurements can better help validate material constitutive models at all length scales. However, limited work has been done characterizing displacements at the micro/nanoscale in the Transmission Electron Microscope (TEM). Here, digital image correlation (DIC) and particle tracking (PT) are applied to measure displacements during in-situ bending experiments of microbeams, either notched or un-notched, prepared by focused ion beam milling. Gold nanoparticles are deposited on the samples to serve as features for DIC and PT. Full-field quantitative deformation is then measured as a function of load from in-situ TEM images of the pattern evolution. To characterize creep behavior a constant load is applied and strain evolution is monitored. A 2D finite element simulation is performed to evaluate material property parameters using an inverse approach. Finally, notched specimens are then used to extract fracture characteristics by comparing numerical with experimental results from DIC and PT.

Using Environmental Transmission Electron Microscopy to Understand the Fundamentals of Metal Oxidation: Eric Stach1; 1University of Pennsylvania
    Professor Ian Robertson pioneered the use of environmental transmission electron microscopy (ETEM) to understand both how metals oxidize, and how these effects can alter mechanical performance. In this presentation, I will review studies conducted with the aberration-corrected ETEM at the Center for Functional Nanomaterials (CFN), Brookhaven National Laboratory. Aberration correction allows routine, readily interpretable atomic-scale imaging of the initial stages of oxidation. The instrument at the CFN was exploited by a number of research groups to explore these effects in Cu, Al, AuCu alloys as well as in nanoparticles systems used in heterogeneous catalysis. These studies have explored such important aspects as the fundamentals of oxide nucleation, oxidation kinetics, and the role of surface crystallography and defect formation play in these processes.

Seeing in 3D and 4D - Advancing the Understanding of Recrystallization: Dorte Juul Jensen1; 1Technical University of Denmark
    The impact that 3D (x,y,z) and 4D (x,y,z,time) X-ray experimental methods have had on the understanding of recrystallization of deformed metals are presented. Well-planned experiments on nucleation and grain boundary migration are reviewed with focus on information gained, which could not have been obtained by traditional 2D methods. This includes new results on particle stimulated nucleation, and effects of the deformation microstructure morphology on boundary migration. It has however also been found that the 3D/4D X-ray measurements sometimes happen to reveal phenomena, which were not expected and therefore not planned to investigate. This includes new results on dislocation structures and residual stress inside recrystallizing grains. Finally, results of 1-1 combinations of experimental results and phase field / molecular dynamics simulations of recrystallization are discussed, and a refined nucleation theory is suggested.

Zinc-Aluminum-Magnesium Coatings for Automotive Industry: Corrosion Analysis on Cross-sections via a New Scanning Electrochemical Microscopy Technique : Marilia Bolsanello1; Javier Izquierdo2; Rejane Maria da Silva1; Ricardo M. Souto2; Jesualdo Luiz Rossi1; Andrea Abreu2; 1IPEN/CNEN-SP; 2Universidad de La Laguna
    Corrosion-resistant coated steels are the stake of the automotive industry in the construction of smarter and more sustainable vehicles. In this field, Zinc-Aluminum-Magnesium coatings enhance zinc cathodic protection of galvanized steels and contribute to a self-repairing effect on scratches and at the cross-sectional area, a crucial region under corrosive agents. In the industrial process, coated sheets are cut and stamped, so the substrate is exposed to corrosive agents at the cut edges. A novel methodology for the spatially resolved measurements with Scanning Electrochemical Microscopy is presented, concerning coated materials during corrosion processes. A new layout for the electrochemical cell was designed, allowing the exposition of both the cross-section and the metal surfaces to the electrolyte. In this way, the access of the ultramicroelectrode tip to the cross-sectional surface is enabled, and so the identification of chemical species in localized corrosion processes with high spatial resolution.

Various Hydrogen/Deuterium Charging Methods for Site Specific APT Specimens: Heena Khanchandani1; Leigh Stephenson1; Dierk Raabe1; Stefan Zaefferer1; Baptiste Gault1; 1Max Planck Institute for Iron Research
     Deterioration in mechanical properties of materials due to hydrogen is called hydrogen embrittlement, which often leads to their catastrophic failures. In order to understand the mechanisms of hydrogen embrittlement and mitigate its influence, it is necessary to examine the role of defects in materials such as grain boundaries, dislocations and stacking faults, as hydrogen trapping sites. We will present two different charging routes for charging the site-specific APT specimens with deuterium in this talk, i.e., the cathodic charging in an electrolytic cell and the gas charging in a Reacthub Module. We will discuss the workflows involved in both the charging methods and the preliminary results concerning the deuterium charging of a TWIP steel specimen [1]. References:1. Stephenson LT, et al. (2018) The Laplace Project: An integrated suite for preparing and transferring atom probe samples under cryogenic and UHV conditions. PLoS ONE 13(12): e0209211.