Integration between Modeling and Experiments for Crystalline Metals: From Atomistic to Macroscopic Scales III: Session III
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
Tuesday 2:00 PM
October 19, 2021
Room: B246
Location: Greater Columbus Convention Center
Session Chair: Bjorn Clausen, Los Alamos National Laboratory; Ben Morrow, Los Alamos National Laboratory
2:00 PM Invited
In-situ Scattering Experiments Facilitating Development and Validation of Constitutive and Process Models: Bjorn Clausen1; Donald Brown1; D. Travis Carver1; 1Los Alamos National Laboratory
Highly penetrating X-ray and neutron beams available at user facilities provide means to evaluate changes in materials in-situ during thermomechanical testing and processing. The non-destructive techniques provides detailed material information at length scales ranging from atomic sizes (a few angstroms, e.g. diffraction) to the mesoscopic regime (about a micrometer, e.g. small angle scattering), as well as the bulk (e.g. texture, phase fractions and porosity). From an experimental point of view challenges in successfully applying these techniques lies in matching the probe characteristics with the material characteristics, as well as matching the time scales of the data collection and the process to be followed. For the modeling, it becomes important to get information that is relevant to parameters and physics that are included in the models, both for required inputs and for the predicted behavior during the loading/processing. The talk will present examples of successful applications, and discuss challenges faced.
2:40 PM
Effect of Twin-twin Junctions on Slip-twin Interactions and Twin-twin Intersections: Jiaxiang Wang1; M.Arul Kumar2; Krishna Yaddanapudi3; Subhash Mahajan3; Irene Beyerlein1; 1University of California, Santa Barbara; 2Los Alamos National Laboratory; 3University of California, Davis
Twin-twin junctions (TTJs) can form in hexagonal close packed metals when multiple twin variants are activated in a grain. A TTJ can have distinctive effects on microscopic slip behavior and macroscopic deformation response compared to those by isolated or closely parallel twins. Here, a full-field crystal plasticity elasto-viscoplastic fast-Fourier transform model incorporating a dislocation density-based hardening law is employed to investigate the twin-twin interactions involved in TTJ formation and the effect of TTJs on slip-twin interactions. We focus our studies on the most commonly observed co-zone twin junction of {10-12} tensile twins in an Mg-Y alloy. For this case, we compute the evolution in the local micromechanical fields and underlying accumulation of dislocation densities for different slip modes during the formation of TTJs. These local fields, particularly dislocation densities, are compared with TEM analyses of TTJs in Mg-Y alloys to help gain insight into how twin-twin junctions develop under stress.
3:00 PM
The Interactions between Basal-precipitates and Propagating Twin Tips in AZ91: Brandon Leu1; Mariyappan Kumar2; Irene Beyerlein2; 1University of California-Santa Barbara; 2Los Alamos National Lab
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.
3:20 PM
Fluctuations in the Generalized Planar Fault Energy Landscape in Concentrated FCC Solid Solutions: Matthew Daly1; Ritesh Jagatramka1; Chu Wang1; 1University of Illinois-Chicago
The generalized planar fault energy landscape provides a roadmap for understanding the intrinsic competition between deformation mechanisms in metals and alloys. Our previous work has demonstrated how fault energies can be leveraged to build scalable physical models that predict the evolution of deformation twin microstructures and strain partitioning amongst deformation mechanisms in FCC metals. Here, we will discuss an expansion of this effort to include concentrated FCC solid solutions. In particular, we will overview the connection between local chemical disorder and stochastic fluctuations in the generalized planar fault energy landscape, along with the effects of these fluctuations on mechanism competition. Efforts to adapt deformation models to account for stochastic fault energies and methods to provide a priori predictions of fault energy fluctuations will also be discussed.
3:40 PM
First-principles Study of the Effect of Al and Hf Impurities on Co3W Antiphase Boundary Energies: Chiraag Nataraj1; Ruoshi Sun2; Christopher Woodward3; Axel van de Walle1; 1Brown University; 2University of Virginia; 3Air Force Research Lab
The effects of Al and Hf impurities on the (111) antiphase boundary (APB) energy of metastable FCC Co3W are investigated via ab initio calculations. Cluster expansions are used to predict the total energies of supercells containing non-dilute concentrations of impurities using Monte Carlo simulations at relevant temperatures. Two sets of compositions are explored for each system — constant ratio and sacrificial W. It is found that sacrificial W compositions are far more stable than constant ratio compositions and Hf increases the APB energy far more than Al. Additionally, at higher concentrations of Hf, Hf and W tend to segregate into alternating planes, unlike the Co-W-Al system, which explains the different impacts of the two impurities on the APB energy. Finally, the ratio of (111) to (100) APB energies is studied for sacrificial W compositions to understand cross slip behavior in both ternary systems.
4:00 PM
Thermodynamic Modeling of the Ga-Ni System Using the Third Generation Gibbs Free Energy Function for Pure Elements: Liangyan Hao1; Chen Shen2; Hongbin Zhang2; Wei Xiong1; 1University of Pittsburgh; 2Technische Universität of Darmstadt
Ni-Mn-Ga alloys are important functional materials due to the magnetic shape memory and magnetocaloric effects. In order to develop a multicomponent thermodynamic database for the Ni-Mn-Ga-based materials, thermodynamic modeling of the Ga-Ni system has been performed through a coupling of ab initio calculations and the CALPHAD method supported by experiments. Particularly, the third generation data for pure elements are considered to better describe the low-temperature thermodynamics and magnetic properties. Available experimental data of phase equilibria and thermodynamic properties are critically reviewed. The composition dependence of the Curie temperature and magnetic moment of the fcc solution phase are predicted by the ab initio calculations, and further utilized as the input for an improved magnetic model to evaluate the magnetic ordering energy. The optimized thermodynamic parameters can successfully reproduce the Ga-Ni phase diagram down to 0 K. The present thermodynamic modeling can serve as a basis for the Ni-Mn-Ga thermodynamic database.
4:20 PM Invited
Co-development of Experiment and Simulation to Observe Dynamic Behavior in Metals in Complex Loading Environments: Benjamin Morrow1; Virginia Euser1; Clarissa Yablinsky1; Nicholas Denissen1; 1Los Alamos National Laboratory
Materials subjected to dynamic conditions often exhibit complex behaviors beyond what is expected in the quasi-static regime. Due to the short timescales involved during dynamic testing, plasticity and phase transformation phenomena are often difficult to capture experimentally, and simulations are required to fill in missing information, specifically regarding evolution of the microstructure and activity of various deformation mechanisms. The challenges of model validation in the dynamic regime will be discussed with case studies showcasing real-world examples of experimental-theoretical linkages. Kolsky bar experiments were paired with mesoscale models for off-equilibrium mechanical behavior. Additionally, experimental measurements and coupled multiphysics modeling were used to enable friction measurements across a wide range of sliding velocities (10^-4 – 20m/s) for structural metals. These examples demonstrate that a co-validation scheme where experiment and theory are used in tandem can be used to access complex datastreams, providing better data/analysis than either could independently, especially for off-nominal conditions.