Integration between Modeling and Experiments for Crystalline Metals: From Atomistic to Macroscopic Scales III: On-Demand Oral Session I
Program Organizers: Arul Kumar Mariyappan, Los Alamos National Laboratory; Irene Beyerlein, University of California, Santa Barbara; Levente Balogh, Queen's University; Caizhi Zhou, University of South Carolina; Lei Cao, University of Nevada; Josh Kacher, Georgia Institute of Technology
Friday 8:00 AM
October 22, 2021
Room: On-Demand Room 7
Location: MS&T On Demand
Session Chair: Jon Molina-Aldareguia, Imdea Materials Institute; M Arul Kumar, Los Alamos National Laboratory
Invited
Yield Point Phenomena in Single Crystal BCC and FCC Metals: David Fullwood1; Josh Tsai1; Tristan Russell1; Guowei Zhou2; Robert Wagoner3; Eric Homer1; 1Brigham Young University; 2Shanghai Jiao Tong University; 3Ohio State University
Yield point phenomena (YPP) are often attributed to locking of dislocations by atmospheres of interstitials, or are related to the increased stress required to nucleated dislocations relative to the subsequent stress required to move them. The orientation dependence of YPP has been observed previously, but not necessarily fully explained. We observe YPP in high-purity single crystal tantalum (BCC) and nickel (FCC) for a range of orientations. An Schmid factor-based activity index is defined to capture the number of slip system likely to be operating. The magnitude of YPP shows a linear correlation with this activity index. Furthermore, a general mesoscale (GM) model that incorporates internal stress generation into a standard crystal plasticity (CP) model, predicts the observations without any fitting to the experimental data (beyond the standard CP hardening parameters). The results point to a role for internal stress evolution in YPP and hardening stagnation for some materials.
Two-scale Simulation of Plastic eformation in BCC Metals: Combination of Atomistic Simulation and Dislocation Dynamics: Sergei Starikov1; Vasily Tseplyaev2; Matous Mrovec1; 1ICAMS, Ruhr University Bochum; 2Grunberg Institut and Institute for Advanced Simulation
It is known that one of the basic mechanisms of plasticity is a motion of dislocations under applied stress. In this work, on the example of Mo and Nb, the study of plastic deformation in bcc metals was performed with multi-scale modelling. The temperature-dependent mobility functions of screw and edge dislocations were calculated from molecular dynamics simulation. The simulations of screw dislocation movement under applied shear stress revealed that the process can proceed in two different regimes: through thermally activated motion and athermal motion. Hence, the dislocation velocity depends on the shear stress in a non-trivial way. The calculated data were implemented in the dislocation dynamics model. Such model allows to simulate plastic deformation taking into account temperature effect on the dislocation mobility.
Transformation-induced Plasticity in Omega Titanium: Amir Hassan Zahiri1; Jamie Ombogo1; Tengfei Ma1; Pranay Chakraborty1; Lei Cao1; 1Universitiy Of Nevada Reno
ω-titanium (Ti) is a high-pressure phase that is conventionally perceived to be brittle and nondeformable, although direct investigations of its deformation process remain scarce. In this work, we perform molecular dynamics simulations to study the deformation process of ω -Ti with initial defects and find that stress-induced ω→α martensitic transformation can cause extensive plasticity in ω -Ti under various loading directions. Moreover, for the first time, we demonstrate that four types of transformation twins—{112 ̅1}, {112 ̅2}, {101 ̅2}, and {101 ̅1}twins—can be formed through the ω→α martensitic phase transformation. This work advances the understanding of plastic deformation in ω -Ti and unveils the essential role of the metastable ω -phase in the formation of transformation twins.
Combining DICTRA Simulations with In-situ TEM Experiments to Optimize Metallic Powder Heat Treatments: Kyle Tsaknopoulos1; Matthew Gleason1; Grace Fitzpatrick-Schmidt1; Danielle Cote1; 1Worcester Polytechnic Institute
In solid-state additive manufacturing, controlling the microstructure of metallic feedstock material is crucial, as it directly influences the properties of the final parts. Thermal processing is often used as a means of microstructural manipulation, tailoring the size, morphology, and distribution of secondary phases for desired material performance. In this study, heat treatments of Al 6061 powder are explored, with particular focus on associated phase transformations and diffusion kinetics, for end use in cold spray (CS) applications. In-situ transmission electron microscopy (TEM) heating experiments are leveraged to closely monitor the powder’s microstructural evolution as a function of treatment time and temperature. The time-morphology data of secondary phases procured from this experimentation can assist with the calibration and validation of DICTRA models. These models will allow for the optimization of heat treatment parameters, prediction of powder microstructures, and understanding of powder heat treatment effects on CS deposition and deposit properties.
Interactions between Dislocations and 3D Interfaces in a Cu/Nb System: Shuozhi Xu1; Justin Cheng2; Zezhou Li2; Nathan Mara2; Irene Beyerlein1; 1University of California, Santa Barbara; 2University of Minnesota, Twin Cities
In metallic systems, 3D interfaces are heterophase interfaces that extend out of plane into the two crystals. Unlike 2D sharp interfaces across which the material properties change abruptly, the 3D interfaces provide a smoother intergranular transition in material properties. In addition, a 3D interface itself is chemically and crystallographically dissimilar from the two crystals that join. While many numerical studies of the interactions between dislocations and 2D interfaces have been conducted, much fewer efforts were devoted to 3D interfaces in the same context. Here, we focus on the nanolayered Cu/Nb containing interfaces with 3D character. The interactions between dislocations and 3D interfaces are simulated via a phase-field dislocation dynamics (PFDD) method informed by atomic-level calculations. In PFDD, the heterogeneities with a general geometry and plastic deformation on general slip planes progress hand in hand. Selected simulation results are benchmarked against atomistic simulations and analytical solutions.
Automated Laue Pattern Analysis for Bragg Coherent Diffraction Imaging: Yueheng Zhang1; Anthony Rollett1; Robert Suter1; 1Carnegie Mellon University
The 34-ID-C beamline at the APS has recently acquired the capability to conduct Laue diffraction, a technique in which a polychromatic X-ray source illuminates a crystal, causing multiple reflections to simultaneously fulfill the Bragg condition and casting a unique Laue pattern on a detector. By rastering this beam across a polycrystalline sample, Laue patterns can be collected from all grains in a region of interest. When many grains are illuminated at the same time, multiple Laue patterns appear on the detector, complicating the process of identifying and indexing the correct set of peaks. We demonstrate automated Laue pattern analysis for segregating overlapping Laue patterns by sorting peaks into groups based on the peaks center-of-mass, indexing all peaks in each separated group, and combining the results to build an orientation map of the microstructure. This tool will also allow us to intelligently conduct coherent X-ray diffraction experiments on grains of interest.