Advanced Characterization Techniques for Quantifying and Modeling Deformation: Session VII
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
Thursday 8:30 AM
March 23, 2023
Room: Aqua 311A
Location: Hilton
Session Chair: Robert Wagoner, Ohio State University; Rui Feng, National Energy Technology Laboratory
8:30 AM Invited
Superior High-temperature Strength in a Supersaturated Refractory High-entropy Alloy: Rui Feng1; Bojun Feng2; Michael Gao3; Chuan Zhang4; Joerg Neuefeind1; Jonathan Poplawsky1; Yang Ren5; Ke An1; Michael Widom2; Peter Liaw6; 1Oak Ridge National Laboratory; 2Carnegie Mellon University; 3National Energy Technology Laboratory; 4CompuTherm LLC; 5Argonne National Laboratory; 6The University of Tennessee, Knoxville
Refractory high-entropy alloys (RHEA) show promising applications at high temperatures. However, achieving high strengths at elevated temperatures above 1,173K is still challenging due to heat softening. Using intrinsic material characteristics as the alloy-design principles, a single-phase body-centered-cubic (BCC) CrMoNbV RHEA with high-temperature strengths (beyond 1,000 MPa at 1,273 K) is designed, superior to other reported RHEAs as well as conventional superalloys. The origin of the high-temperature strength is revealed by in-situ neutron scattering, transmission-electron microscopy, and first-principles calculations. The CrMoNbV’s elevated-temperature strength retention up to 1,273 K arises from its large atomic-size and elastic-modulus mismatches, the insensitive temperature dependence of elastic constants, and the dominance of non-screw character dislocations caused by the strong solute pinning, which makes the solid-solution strengthening pronounced. The alloy-design principles and the insights in this study pave the way to design RHEAs with outstanding high-temperature strength.
9:00 AM
Plasticity of Fused Silica Studied by High-temperature Micropillar Compression and Ptychographic X-ray Computed Tomography: Remo Widmer1; Alexander Groetsch2; Guillaume Kermouche3; Ana Diaz4; Manish Jain2; Rajaprakash Ramachandramoorthy5; Laszlo Pethö2; Jakob Schwiedrzik2; Johann Michler2; Nicholas Randall1; 1Alemnis AG; 2Empa; 3Mines Saint-Etienne; 4Paul Scherrer Institute; 5MPIE
As the miniaturization of fused-silica micro-components progresses, we need to understand and predict this material’s micro-scale plasticity. Displacement-controlled micropillar compression test at high temperatures up to 600 °C and variable strain-rates up to 1 s-1 was followed by synchrotron-based ptychographic X-ray computed tomography (PXCT) with a spatial resolution of 23 nm3 and absolute density measurement with an accuracy of +/- 0.025 g/cm3. The deformation mechanisms appear to transition as follows: Shear-localization and shear-promoted densification at 25 °C; homogeneous shear-flow and densification limited by radial cracking at 300 °C; and unconstrained shear-flow and limited densification due to weak confinement strength at 600°C. These results provide a new perspective on the interplay of various deformation mechanisms that accommodate plasticity in fused silica, and their temperature-dependence. Meanwhile, PXCT is demonstrated to be a powerful tool that matches the requirements in spatial resolution and contrast for studying plasticity enabling mechanisms in amorphous materials.
9:20 AM
Amorphization of Covalently-Bonded Solids by Laser Shock Compression: A Generalized Deformation Mechanism under Extreme Conditions: Boya Li1; Alex Li1; Shiteng Zhao2; Marc Meyers1; 1University Of California San Diego; 2Beihang University
Laser shock compression subjects materials to an extreme regime of high quasi-hydrostatic pressure and high strain rates. The mechanisms of plastic deformation in metals whereby dislocations, twins, and phase transitions. Covalently bonded materials, however, have great difficulty in responding by conventional plastic deformation due to the directionality of their bonds. We propose that the shear from shock compression induces amorphization, as observed in Si, Ge, B4C, SiC, olivine ((Mg, Fe)2SiO4), diamond, and perovskite (CaTiO3) and that this is a general deformation mechanism in a broad class of covalently bonded materials. SEM, FIB and TEM are used to characterize microstructure of the shocked targets, and electron diffraction patterns can confirm the crystal structure of materials. Molecular dynamics simulations are effective to study the motions of atoms and molecules in materials. The three-pronged approach, employing experimental, analytical, and computational methods, has enhanced our understanding of the response of materials under extreme conditions.
9:40 AM Invited
How Do Metals Remember Their History?: Robert Wagoner1; Stephen Niezgoda1; David Fullwood2; Guowei Zhou3; Ehsan Taghipour1; 1Ohio State University; 2Brigham Young University; 3Shanghai Jiao Tong University
Scalar metal memory, or isotopic work hardening, is conceptually well understood: Plastic deformation induces dislocation multiplication and intersection, which increases strength microstructurally by higher dislocation density and shorter pin spacing. Tensor metal memory, as sometimes represented macroscopically by kinematic hardening, has no such simple interpretation. Well-known and broad manifestations include the Bauschinger effect, ratcheting in fatigue, back stress in creep, and anelasticity. Recent experiments and simulations suggest that anelasticity and other tensor memory effects are the result of the concurrent operation of two mechanisms: 1) development of internal stress by GND evolution and 2) bowout of dislocation segments. The rapidly-evolving evidence for this hypothesis, some peer-reviewed and published, some in progress or in review, will be summarized. Experimental results for complex commercial alloys as well as for single crystals and bicrystals show that directional hardening is likely significant at all length scales and for all metals. Crystal plasticity simulations with an explicitly calculated internal stress tensor field throughout the body predict the various effects, but often only approximately in terms of magnitude. Integrating dislocation bowout with the existing internal stress capability promises to complete the theory.
10:10 AM Break
10:30 AM
Grain Boundary Deformation and Damage: Veronica Anghel1; Ramon Martinez1; James Valdez1; 1Los Alamos National Laboratory
Damage nucleation in polycrystals occurs in locations of large strain concentrations, or microstructurally, in regions where heterogeneous deformation occurs. Experiments commonly show that cracks and voids tend to develop preferentially in some boundaries but less in others, indicating the significance of heterogeneity in local deformation. Grain boundaries are known to be a critical microstructural component controlling material’s mechanical properties, and their misorientation and crystallographic boundary planes can also influence the dislocation dynamics. Small scale tensile experiments performed on a mini tensile stage in aluminum and tantalum are used to investigate deformation around grain boundaries in columnar-grained metals. In-situ EBSD and DIC measurements looking at active deformation mechanisms and damage nucleation around grain boundaries are employed for detailed analysis of deformation evolution and damage nucleation. Results present influence of grain boundary types, grain boundary orientation with respect to loading, and evolution of dislocation densities around the grain boundaries.
10:50 AM Cancelled
Special In-situ Diffraction Evaluations in Response to High-temperature Plastic Deformation: Klaus-Dieter Liss1; 1Guangdong Technion - Israel Institute of Technology (GTIIT)
Diffractograms by modern neutron and synchrotron sources are nowadays taken with multi-dimensional detectors, while their evaluation lacks behind and often ingrates over some dimenstion in reciprocal space. Here, I like to resume fine-beam high-energy X-ray diffraction following in-situ plastic deformation while evaluating the grain orientation statistical behavior during their microstructural evolution, especial at high temperature. Moreover, in-situ neutron diffraction evaluated by the dynamical theory of diffraction reveals defect kinetics of metals at high temperature.
11:10 AM
Analyzing Mesoscale Stress Localization and Slip System Activation under Axial-Torsional Loading: Jerard Gordon1; 1University of Michigan
While plastic flow under non-uniform deformation has been well-studied using macroscopic analysis, the crystal-scale mechanisms influencing localized deformation under multiaxial strain paths have not been extensively examined. To this end, we performed in-situ high energy diffraction microscopy during solid bar axial-torsional loading to quantify grain-resolved stress states, reorientation, and slip system response in a high-strength, single phase complex concentrated alloy. Overall, von Mises equivalent stress distributions within the sample volume displayed gradient behaviors based on radial position, largely following typical continuum mechanics descriptions. However, no noticeable correlation between grain reorientation and radial position was observed. Comparative analysis of slip system activation in grains with the highest reorientations did not reveal statistically significant increases in the number of active slip systems for axial-torsional loading compared with pure torsion. These findings highlight the complexity of multiaxial load paths on mesoscale response in polycrystals and the need for further advancements in companion modeling.