Advanced Characterization Techniques for Quantifying and Modeling Deformation: Deformation Twinning
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS Structural Materials Division, TMS: Shaping and Forming Committee, TMS: Materials Characterization Committee
Program Organizers: Rodney McCabe, Los Alamos National Laboratory; Thomas Bieler, Michigan State University; Marko Knezevic, University of New Hampshire; Irene Beyerlein, University of California, Santa Barbara; Wolfgang Pantleon, Technical University of Denmark; C. Tasan, Massachusetts Institute of Technology; Arul Kumar Mariyappan, Los Alamos National Laboratory
Monday 2:30 PM
February 24, 2020
Room: Theater A-2
Location: San Diego Convention Ctr
Session Chair: Shujuan Wang, Los Alamos National Laboratory; Philip Eisenlohr, Michigan State University
2:30 PM Invited
More than Crystal Plasticity: Multiphysics in DAMASK: Philip Eisenlohr1; Aritra Chakraborty2; Pratheek Shanthraj3; Martin Diehl4; Darren Pagan5; Thomas Bieler1; 1Michigan State University; 2Argonne National Laboratory; 3University of Manchester; 4Max Planck Institut für Eisenforschung GmbH; 5Cornell University
Decomposing the total deformation gradient into elastic, eigenstrain, and plastic components opens the door to concurrently couple various mechanisms and associated transport phenomena to the standard crystal plasticity solution of mechanical equilibrium. The talk highlights recent advances in implementing staggered solution schemes for heat and mass transport as well as phase field damage that allows concurrent coupling to the solution of mechanical equilibrium for arbitrary elastic, eigenstrain, and plastic material behavior with DAMASK. Examples to demonstrate these capabilities include the variation of the internal stress field during thermal cycling of polycrystalline hexagonal Ti and the stress-driven mass redistribution in plasticallyrelaxing Sn films under thermal stress.
3:00 PM
Microscratch-induced Deformation Twins in Mg Single Crystals: Kehang Yu1; Xin Wang1; Olivia Donaldson1; Subhash Mahajan2; Irene Beyerlein3; Timothy Rupert1; Julie Schoenung1; Enrique Lavernia1; 1University of California, Irvine; 2University of California, Davis; 3University of California, Santa Barbara
Microscratching was developed and implemented as a technique to induce a localized stress field in order to study the behavior of twins in Mg; surprisingly, there are very few published studies using this approach. In this work, the microscratch was performed on a Mg single crystal using different scratch parameters. The microscratched Mg was then characterized with serial sectioning and EBSD to show the twin distribution in a 3D manner. The twin distribution was also predicted based on microscratch-induced stress field calculations using an analytical solution and finite element method (FEM). An experiment-calculation comparison examined the correlation between the local stress field and twin formation. Our results suggest that, by controlling the loading conditions, microscratching is able to generate deformation twins with predicted variant and morphology. Furthermore, forming twin networks or meshes could be made possible with multiple microscratches for the study of twin-twin interactions in Mg.
3:20 PM
Study of the Interplay of Basal Slip Activities and Double Twinning Mechanism in Magnesium Using SEM In-situ Tensile Tests Concurrently with HR-EBSD: Nicolo Maria Della Ventura1; Xavier Maeder1; Szilvia Kalácska1; Thomas Edwards1; Daniele Casari1; Johann Jakob Schwiedrzik1; Johann Michler1; 1Empa
An SEM in-situ uniaxial micro-tensile testing set-up was designed to perform HR-EBSD and HR-DIC during deformation. This set-up was used to study extension twinning mechanism in magnesium. Several micron-sized T-bars were prepared in single crystal magnesium by FIB with a loading direction along the c-axis. HR-EBSD cross correlation is used to map local strains, stresses and GNDs distributions at different deformation steps. Special attention was made in lattice distortion during twin nucleation and thickening. DIC was used to measure total strain and to capture progressive slip and twinning activities during the tests. Basal slip activities occur systematically before twinning despite a low Schmid factor. Extension twin nucleates at proximity to the basal slip location. Extension twins systematically involve into double twins with progressive deformation. Twins shapes and distribution are investigated by post-mortem 3D-EBSD. Post-mortem TEM and TKD are also done to investigate the interplay between slip and double twinning activities.
3:40 PM
In-situ Mapping of Twin Related Local Stress Fields in HCP Titanium: Arul Kumar Mariyappan1; Laurent Capolungo1; Rodney McCabe1; Wenjun Liu2; Jon Tischler2; Carlos Tome1; 1Los Alamos National Laboratory; 2Argonne National Laboratory
Deformation twinning in a crystal results in a significant lattice-reorientation and localized shear in the narrow twin domain; hence heterogeneity in stresses develops at and in the vicinity of twins. These stresses strongly influence further twin growth and de-twinning processes but are extremely difficult to characterize experimentally. In this study, an in-situ synchrotron experiment with differential-aperture X-ray microscopy is performed to measure the 3D stresses in the vicinity of a {10-12} twin in hexagonal close packed titanium with a spatial resolution of 0.5-micron. Rolled and recrystallized titanium with a strong basal-texture is subjected to bending to introduce tensile-twins. The measured stresses help to quantify the heterogeneity associated with twinning and also to characterize the dynamic processes involved with twinning. Under further-straining the twin grows heterogeneously and the local growth correlates well with the measured local stresses. This work significantly advances our understanding of twinning and also guides modeling tool development.
4:00 PM Break
4:20 PM
Three-dimensional Faceted Boundaries of Different Twin Modes in hcp Metals: Shujuan Wang1; Khanh Dang1; Rodney McCabe1; Laurent Capolungo1; Carlos Tome1; 1Los Alamos National Laboratory
In hcp metals, deformation twinning is a major mechanism of shear accommodation. Tensile loading along the c-axis or effective compression perpendicular to the c-axis generally trigger {1012}<1011> and/or {1021}<1126> tensile twins, while compression parallel to the c-axis usually enables {1122}<1123> and/or {1011}<1012> compression twins. The nucleation and growth of these twins are controlled by the three dimensional (3D) faceted structures of their boundaries. We characterized the 3D faceted boundaries of {1012} in Mg and Ti and {1122} twins in Ti at the atomic scale using high-resolution transmission electron microscopy (HRTEM). We find eight characteristic facets in both {1012} and {1122} twin boundaries five and six of which have not been observed before, respectively. Implications of the observed facet structures towards the activation barriers and mobility of these facets will be discussed.
4:40 PM
{10-12} Twin Boundary Segregation of Y in Mg Alloys: Xin Wang1; Yang Hu1; Kehang Yu1; Subhash Mahajan2; Irene Beyerlein3; Enrique Lavernia1; Timothy Rupert1; Julie Schoenung1; 1University of California Irvine; 2University of California, Davis; 3University of California, Santa Barbara
The deformation response of Mg and its alloys is critically influenced, not only by dislocation slip, but also by the nucleation and growth of deformation twins. An atomic scale characterization of the microstructure and chemical composition of twin boundaries (TBs) is therefore an appropriate approach to investigate the underlying mechanisms. In this work, we report on a somewhat unexpected solute segregation phenomenon: Y-rich columns and nanoscale Y-rich clusters segregated at the basal-prismatic (BP/PB) interfaces on {10-12} TBs after a small deformation of a Mg-3wt%Y binary alloy at room temperature. A similar Y-clustering was predicted by a hybrid Monte Carlo/molecular dynamics (MC/MD) method, with the driving force for Y segregation being provided by the misfit between Y atoms and Mg matrix and the tensile stress at the BP/PB interfaces. Segregation of Y to the BP/PB interfaces provides a pinning effect that affects the twinning dynamics and strengthening of Mg-Y alloys.
5:00 PM
Micron-scale Characterization of Twinning and Dislocation Slip in Magnesium Single-crystals by Advanced In-situ Techniques: Kristián Máthis1; Dávid Ugi2; Petr Harcuba1; Michal Knapek1; František Chmelík1; Péter Ispánovity2; István Groma2; 1Charles University; 2Eötvös Loránd University
A rare blend of combination of in-situ scanning electron microcopy (SEM) and acoustic emission (AE) technique has been employed for study the deformation behavior of Mg micropillars. The combination of these two techniques enables to study the underlying physical processes with exceptional spatiotemporal resolution. It is shown that the stress drops on the deformation curves caused by size-effect are in perfect correlation with the acoustic emission events. The internal dynamics of the twinning and dislocation slip is discussed in detail using statistical analysis of the data.
5:20 PM
Antitwinning in Nanoscale Tungsten: Jiangwei Wang1; Ting Zhu2; 1Zhejiang University; 2Georgia Institute of Technology
Nanomaterials often surprise us with unexpected phenomena. Here we report a surprising discovery of the anti-twinning deformation, previously thought impossible, in nanoscale body-centered cubic (BCC) tungsten crystals. By using in situ transmission electron microscopy nanomechanical testing, we observed the nucleation and growth of anti-twins in tungsten nanowires with diameters less than ~ 20 nm. Anti-twinning produces a shear displacement of 1/3<-1-1-1> on every successive {112} plane, in contrast to an opposite 1/6<111> shear by ordinary twinning. This asymmetry in shear geometry leads to a much higher resistance to anti-twinning than ordinary twinning, as shown by first principles calculations. Nonetheless, anti-twinning becomes active in nano-sized BCC crystals that have limited plastic shear carriers and thus develop ultra-high stresses. This work unveils a surprising deformation mode in BCC crystals and has broad implications for harnessing unconventional deformation mechanisms to achieve high mechanical preformation by nanomaterials.
5:40 PM Cancelled
Quantifying Elastic Strain Near Twin Interface in Magnesium with Nanometric Resolution: Jinsong Chen1; Yue Liu1; Jian Wang2; Carlos Tomé3; 1Shanghai Jiao Tong University; 2University of Nebraska-Lincoln; 3 Los Alamos National Laboratory
Localized plastic shear associated with deformation twinning induces both, dislocation emission and elastic strain fields near twin interfaces. We modified a standard peak-pair algorithm (PPA) to extract the local elastic strain field associated with twins in Mg from the observed atomic structure. We also used nano-beam electron diffraction (NBED) method for comparison and to characterize the strain field at several positions inside and near a twin. The results reveal a much larger stress concentration near the basal-prismatic interface than at the coherent twin boundary and a stress concentration in the matrix ahead of the twin tip that seems to be associated with dislocation pile-ups. This work provides insight at the nanometric scale about the elastic strain field associated with both elastic and plastic deformation in the vicinity of twin interfaces. Moreover, the modified PP method is extended to different crystal structures, providing a universal nanometric resolution elastic strain measurement method.