Advanced Characterization Techniques for Quantifying and Modeling Deformation: Session I
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 Underwood Jackson, Sandia National Laboratories

Monday 8:30 AM
February 28, 2022
Room: 207A
Location: Anaheim Convention Center

Session Chair: Balila Jaya, Indian Institute of Technology Bombay; Khalid Hattar, Sandia National Laboratories; Daniel Gianola, University of California-Santa Barbara


8:30 AM  Invited
Imaging Defects and Their Dynamics Using Scanning Electron Microscopy Approaches: Daniel Gianola1; 1University of California-Santa Barbara
    The past several years has witnessed a surging popularity of two techniques for defect characterization in crystalline materials: (i) scanning transmission electron microscopy (STEM) using diffraction contrast imaging, and (ii) electron back-scattered diffraction (EBSD) mapping. Here, we link these capabilities by employing a field emission SEM equipped with a transmission detector for defect characterization – termed transmission SEM (TSEM). Imaging modes that are similar to conventional CTEM bright field (BF) and dark field (DF) and STEM are explored, and some of the differences due to the varying accelerating voltages highlighted. We further demonstrate how the richness of information encoded in EBSD patterns is amplified by a new generation of direct electron detectors that enable high speed mapping and acquisition of high-fidelity patterns that can be used for statistically-meaningful defect analyses. We employ these techniques for in situ tensile experiments to study the nature of dislocations dynamics in several structural alloys.

9:00 AM  
High Temperature In Situ TEM Based Nanomechanical Testing: Shen Dillon1; 1University of California, Irvine
    Room temperature in situ nanomechanical testing has provided significant insights into deformation mechanisms in materials. The vast majority of the work, however, has not been at homologous temperatures relevant to diffusion assisted or diffusion mediated deformation processes. This talk will highlight recent efforts to extend small scale in situ mechanical testing into the high temperature and ultrahigh temperature regimes using laser heating. The talk will discuss applications in metals, ceramics, and metal-ceramic composites.

9:20 AM  
Applications of Direct Detection for EBSD Analysis of Deformed Materials: Matthew Nowell1; Stuart Wright1; William Lenthe1; Rene de Kloe1; 1EDAX LLC
    Electron Backscatter Diffraction has become an essential tool for the characterization of deformed materials. Recent advanced in detector technology have expanded the capabilities of this microanalysis technique. Direct detectors, where the traditional phosphor screen used to convert diffracted electrons into light photons and the optical coupling between the phosphor and the sensor are eliminated, directly capture these electrons with a position-sensitive detector and have recently become available for EBSD applications. These detectors provide high sensitivity and zero distortions. The heightened sensitivity allows operation at lower beam doses which reduce the interaction volume, which can be beneficial when sampling deformed materials. The removal of phosphor and optical distortions and artifacts improves cross-correlation performance for improved angular resolution via HR-EBSD.

9:40 AM  
Role of Misorientation on Grain Boundary Sliding through High-resolution Digital Image Correlation: Alberto Orozco-Caballero1; Eugenia Nieto-Valeiras2; Javier Llorca2; Fernando Carreņo3; 1Polytechnic University of Madrid; 2IMDEA Materials Institute; 3CENIM-CSIC
    Superplastic deformations are likely to occur in fine and highly misoriented microstructures through the activation of the grain boundary sliding (GBS) deformation mechanism. While it is generally proven that the optimum grain size is in the range 1-20 ĩm, corresponding values of misorientation are not stablished. This is mainly due to the experimental difficulties of relating the individual grain to grain misorientation to the overall superplastic deformation. Nevertheless, such limitation can be overcome by means of the recently developed High-Resolution Digital Image Correlation (HRDIC), a displacement mapping technique during mechanical loading that allows quantifying strain localization with resolutions bellow 100 nm. The material used in the present work is an overaged Al 7075 alloy subjected to severe friction stir processing in order to obtain a microstructure prone to GBS. The statistical HRDIC analysis of the sliding at individual boundaries allowed to determine the relative influence of misorientation on superplastic deformation.

10:00 AM Break

10:15 AM  Invited
Exploring Nanoscale Fatigue through Coupled In-situ Microscopy and Modeling: Khalid Hattar1; Christopher Barr1; Ta Duong2; Daniel Bufford1; Abhilash Molkeri2; Nathan Heckman1; David Adams1; Ankit Srivastava2; Michael Demkowicz2; Brad Boyce1; 1Sandia National Laboratories; 2Texas A&M University
    Coupling in-situ experiments with predictive modeling permits the ability to gain synergistic insight beyond that which is possible by either alone. Recent advancements in Automated Crystal Orientation Mapping (ACOM) and quantitative in-situ transmission electron microscopy (TEM) techniques provide increased capability to directly couple the experimental results to both molecular dynamic simulations and meso-scale modeling. This presentation demonstrates the recent experimental and modeling approach to fully understand the response of high purity nanocrystalline metals to in-situ TEM high-cycle fatigue. In addition to the typical refinement and validation loop between modeling and experiments, this work utilized digital twin systems created from the experimental ACOM data with slight alterations in the stacking fault energy, grain boundary relationships, and crack parameters to elucidate the factors governing the observed crack healing mechanisms observed during the in-situ fatigue experiments. SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525.

10:45 AM  
Significant Disparity of Deformation Behavior in Hot-rolled Highly-textured Mg and Mg-3Al-1Zn Alloy under Tension: Kelvin Xie1; Dexin Zhao1; 1Texas A&M University
    In this work, we deformed hot-rolled highly-textured pure Mg and AZ31 samples with similar initial microstructures under tension along the rolling direction. Apparent shear banding was only observed in the pure Mg samples from the early stage of the deformation. Systematic tilting experiments with transmission electron micropscopy and statistical analyses of multiple grains at different strain levels revealed a significant disparity of non-basal dislocation activities between pure Mg and AZ31. For pure Mg, <c+a> dislocations were activated since the early stage of plastic deformation. For AZ31, <c+a> dislocations were mostly absent at all strain levels, even in the strain-to-failure samples. Non-basal <a> dislocations, including prismatic and pyramidal <a> dislocations, were observed. The promotion of the non-basal <a> dislocation activities and the suppression of <c+a> dislocations in AZ31 are expected to offer more sustainable hardening, which could elucidate the absence of apparent shear banding and much-improved ductility in AZ31.

11:05 AM  
In Situ Study of Kink Banding in Cu/Nb Nanolaminates: Yifan Zhang1; Nan Li1; Matthew Schneider1; Laurent Capolungo1; Rodney McCabe1; 1Los Alamos National Laboratory
    Nano metallic laminates (NMLs) have distinct failure modes due to their inherent mechanical property anisotropies. Kink banding is one of the common failure modes observed in NMLs under layer-parallel compression. However, an in-depth understanding of the mechanisms of kink band formation is currently lacking. In this work, deformation behaviors of Cu/Nb NMLs are investigated by in situ micro pillar compression along a layer-parallel direction. The nucleation and propagation of kink bands in Cu/Nb NMLs are recorded and analyzed with respect to the stress-strain responses. Post-mortem S/TEM, TKD, and HR-EBSD analyses reveal a hierarchical microstructural evolution and defect distribution induced by kink banding. For instance, abundant low angle grain boundaries and geometrical necessary dislocations were observed near the kink band boundaries.

11:25 AM  
Strain Rate Dependent Deformation and In-situ TEM Crystallization in Crystalline/Amorphous Ni-Zr Thin Films: Bibhu Prasad Sahu1; Amlan Dutta2; Rahul Mitra2; 1University of Michigan; 2Indian Institute of Technology Kharagpur
    The three different composition of Ni-Zr thin films having different crystalline and amorphous phase fraction has been studied for nano-indentation creep behaviour at a range of loading strain rates. Time-dependent relaxation during different loading rates has a great effect on the evolution and disappearance of shear bands along with the nanocrystallization during indentation of the crystalline as well as amorphous Ni-Zr thin films. Further, the stages of crystallization of the amorphous Ni-Zr film have been investigated by differential scanning calorimetry (DSC) and in-situ annealing in a high resolution transmission electron microscopy (HRTEM). The difference in crystallization behaviour of the amorphous film in ex-situ DSC experiment from that of in-situ TEM observation is attributed to structural relaxation with reduction of free volume during thermal activation. Interestingly, the in-situ HRTEM annealing of the amorphous film gives the evidence of grain rotation as well as twinning-detwinning phenomena during the intermediate stages.