Advanced Characterization Techniques for Quantifying and Modeling Deformation: Session III
Sponsored by: TMS Extraction and Processing Division, TMS Structural Materials Division, TMS: Advanced Characterization, Testing, and Simulation Committee, TMS: Materials Characterization Committee
Program Organizers: Mariyappan Arul Kumar, 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

Tuesday 8:00 AM
March 1, 2022
Room: 207A
Location: Anaheim Convention Center

Session Chair: Michael Tonks, University Of Florida; Rodney McCabe, Los Alamos National Laboratory

8:00 AM  Invited
A 3D Microstructure Evaluation Tool for Interface Statistics: An Application to Deformation Twins: Rodney McCabe1; Patrick Pinney1; Renuka Gogusetti1; M Arul Kumar1; Carlos Tomé1; Laurent Capolungo1; 1Los Alamos National Laboratory
    Large scale microstructure statistics based on polished two-dimensional metallographic sections have been invaluable for describing microstructure correlations associated with deformation twinning. However, these 2D analyses cannot explicitly capture microstructure characteristics that are inherently three-dimensional, such as: individual grain/twin size and morphology, misorientation and boundary plane normal of grain boundary, twin domain facets, and full neighborhood effects. We have developed a new method for generating 3D datasets coupling polarized light microscopy (PML) with electron backscatter diffraction (EBSD) for 3D serial sectioning of ~mm3 volumes with ~300nm spatial resolution. In addition, we have developed a 3D graph theory based tool to analyze twinning statistics from these data sets and others such as 3D-EBSD generated using focused ion beam (FIB) based techniques. Based on these two capabilities, we will demonstrate 3D microstructure effects on deformation twinning in high-purity titanium.

8:30 AM  
Martensitic Transformation-mediated Twin Nucleation in Hexagonal Close Packed Metals: Lei Cao1; Amir Hassan Zahiri1; Jamie Ombogo1; 1University of Nevada
    Though twinning plays an equally vital role to that of dislocation slips in accommodating deformation in hexagonal close packed crystal structure, its atomic-level nucleation mechanism has long been under debate. Accordingly, there is a critical need to rigorously understand the atomic mechanism of twin nucleation. We performed large-scale molecular dynamics simulations to study the deformation process in hexagonal close packed magnesium and titanium. We found the nucleation of various deformation twins through reversible martensitic phase transformations, via evanescent intermediate phases. Our findings are crucial for completing the twinning theories in hexagonal close packed metals.

8:50 AM  
Investigation of Grain Size Effects on Cyclic Deformation and Twinning in Magnesium Alloys by High Energy X-ray Diffraction: Duncan Greeley1; Mohammadreza Yaghoobi1; Katherine Shanks2; Darren Pagan2; Veera Sundararaghavan1; John Allison1; 1University of Michigan; 2Cornell High Energy Synchrotron Source
    The grain size distribution in polycrystalline materials has a significant impact on yield and flow stress during deformation. Plastic cyclic deformation in magnesium alloys is accommodated by a mix of dislocation slip and twinning depending on sample texture and loading conditions and understanding the impact of grain size on activity of individual deformation modes is important for accurately modeling fatigue behavior. Compression-tension cyclic deformation was characterized in Mg-4wt.%Al and Mg-2.4wt.%Nd binary alloys under multiple grain size conditions using High Energy X-Ray Diffraction Microscopy (HEDM) at the Cornell High Energy Synchrotron Source (CHESS). Grain-scale cyclic twinning and detwinning, basal, prismatic, and pyramidal II <c+a> slip mode critical resolved shear strength, and the evolution of sample texture were tracked using far-field HEDM and near-field HEDM. The impact of grain size on the evolution of deformation during cyclic displacement was investigated and simulated with the PRISMS-Plasticity crystal plasticity finite element software.

9:10 AM  
Statistical Analysis of Forward and Lateral Transmission of Twins Across Grain Boundaries in HCP Magnesium: Mariyappan Arul Kumar1; Rodney McCabe1; Laurent Capolungo1; Carlos Tome1; 1Los Alamos National Laboratory
    A detailed statistical analysis of twin-transmission in the forward (along the twinning shear-direction) and lateral (along the direction perpendicular to both twinning plane-normal and shear-direction) directions is performed in rolled magnesium compressed along the rolling-direction (RD). EBSD images are acquired from two different cuts: a section containing the RD and normal-directions (ND) to analyze forward twin-transmission; and a section with a normal at 45 to the RD and ND to capture lateral twin-transmission. A statistical analysis of EBSD microstructures comprising thousands of twins provides the following key findings. Twinning transmission propensity decreases with increasing grain-boundary (GB) misorientation angle for both forward and lateral directions. Twin-transmission is relatively more favorable in the lateral direction compared to forward direction, and thus leads to longer twin chains in the lateral side than the forward side. GB mis-orientation axis does not seem to influence the twin-transmission for either forward or lateral transmission.

9:30 AM Break

9:45 AM  Invited
Considering the Impact of Anisotropy on Microcracking in Brittle Materials Using the Phase Field Fracture Model: Michael Tonks1; Shuaifang Zhang2; Aashique Rezwan3; Andrea Jokisaari4; Wen Jiang4; 1University of Florida; 2Oak Ridge National Laboratory; 3University of Wisconsin-Madison; 4Idaho National Laboratory
    Microcrack formation and propagation is highly dependent on the microstructure of the material and on the anisotropic material behavior. In this presentation, we summarize various recent developments in phase field fracture models that add the capability to model material anisotropy and its impact on brittle fracture at the mesoscale. We start by considering the impact of elastic anisotropy. We then include the impact of preferred cleavage planes. We end by considering thermal fracture induced by anisotropic thermal expansion coefficients. Simulations are carried out in 2D and 3D. All simulation results are obtained using the MOOSE framework.

10:15 AM  
On the Correlation between Plastic Strain and Misorientation in Polycrystalline Body-centered-cubic Titanium Alloys: An Experimentally and Numerically Study: Vahid Khademi1; Thomas Bieler1; Masahiko Ikeda2; Carl Boehlert1; 1Michigan State University; 2Kansai University
    It is well-known that the level of geometrically necessary dislocations increase with an increase in plastic strain. Hence, it is expected that the level of crystallographic misorientation also increases with plastic strain, which has been observed in face centered cubic alloys. In this study, the correlation between misorientation and plastic strain was studied experimentally and numerically on two body centered cubic titanium alloys. Eleven room-temperature tensile experiments were performed inside a scanning electron microscope. The results, which included electron backscattered diffraction orientation maps performed at different plastic strains, revealed a linear correlation between misorientation and plastic strain, regardless of the reference orientations, as long as the plastic strain was uniformly distributed throughout the gage section, i.e., the necking did not occur in the sample. Furthermore, it was found that samples, which were incrementally loaded through different strain levels, experienced a higher level of misorientation compared with monotonically-tested samples.

10:35 AM  
NOW ON-DEMAND ONLY – The Effects of Precipitates on Twinning in Mg Alloys: Brandon Leu1; M Arul Kumar2; Kelvin Xie3; Irene Beyerlein1; 1University of California, Santa Barbara; 2Los Alamos National Laboratory; 3Texas A&M University
    Precipitates have shown to strengthen Mg-alloys by blocking dislocation glide. However, the interactions between these precipitates and commonly occurring deformation twins is much less understood. Here, an elasto-viscoplastic fast-Fourier-transform (EVP-FFT) model is used to study the interactions between plate-shaped basal precipitates and twins in Mg-Al alloys. Our results suggest that while precipitates may impede the propagation and growth of twin, they can also cause stress localizations that promote the nucleation of multiple new twins. The location of the twin-precipitate interaction site and the size of the precipitate are shown to influence the propensity for new twins to develop. Depending on the twin-precipitate impingement site, we propose various twinning pathways that may help explain how twins can proliferate the matrix in the presence of precipitates.

10:55 AM  
Experimental Characterization and Explicit Slip Band Micromechanical Modeling of Slip Localization in FCC and HCP Metals: Behnam Ahmadikia1; Jean Charles Stinville1; Tresa Pollock1; Irene Beyerlein1; 1University Of California Santa Barbara
    Recent advances in microscopy and digital image correlation methods have enabled quantitative features of slip bands, such as localization intensity and slip band spacing, to be characterized in a vast range of materials including FCC and HCP metals. Experimental measurements reveal that, regardless of crystal structure, a material with a higher yield strength tends to have larger amplitudes of slip localized within slip bands with wider spacings. A slip-band full-field fast Fourier transform-based model is applied to determine the propensity for slip localization in these materials and to investigate the resulting changes in local stress and strain fields. Modeling results find that, in a stronger material, while slip accommodation within the slip band reduces resistance for further slip to glide by a greater degree, the area affected by a reaction stress developed around a fully formed band is larger, making it more difficult for a new band to form nearby.