Deformation Mechanisms, Microstructure Evolution, and Mechanical Properties of Nanoscale Materials: Interface and Grain Boundary Effects
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS: Nanomechanical Materials Behavior Committee
Program Organizers: Niaz Abdolrahim, University of Rochester; Matthew Daly, University of Illinois-Chicago; Hesam Askari, University Of Rochester; Eugen Rabkin, Technion; Jeff Wheeler, Femtotools Ag; Wendy Gu, Stanford University
Thursday 2:00 PM
March 23, 2023
Room: Aqua 300AB
Location: Hilton
Session Chair: Fadi Abdeljawad, Clemson; Douglas Spearot, University of Florida
2:00 PM Invited
Theoretical and Machine Learning Studies of Grain Boundary Solute Drag in Nanocrystalline Alloys: Fadi Abdeljawad1; Malek Alkayyali1; 1Clemson University
Even minute amounts of solutes at grain boundaries (GBs) lead to drastic changes to GB dynamics. Of particular interest is how GB solute segregation influences boundary migration in nanocrystalline alloys. While GB segregation has been shown to mitigate grain growth in such alloys, most studies are focused on the thermodynamic aspect of segregation and the role of dynamic solute drag remains poorly understood. Herein, we develop a solute drag model in nanocrystalline alloys, which explicitly accounts for solute-solute interactions in both the bulk and GBs. Further, the model captures at a phenomenological level the impact of GB structure and its influence on segregation behavior. Computational and machine learning studies employing neural networks are used to explore the solute drag hypersurface and identify regimes with maximum drag effects. A universal solute drag-velocity relation is proposed that provides a robust fit for alloys with various chemical interactions and compositions.
2:30 PM
Heterostructured Interfaces in Lamellar Metallic Composites (LMCs) and Their Contribution to Materials Properties on Different Length Scales: Moritz Kuglstatter1; Heinz Werner Höppel1; Mathias Göken1; 1Friedrich-Alexander-Universität Erlangen-Nürnberg
Heterostructured materials recently gained increasingly attention, as they offer high potential for surpassing materials properties of conventional engineering materials. An in-depth understanding of the contribution of versatile heterostructural combinations is essential to bury this treasure. Effects of heterostructures are often also denoted as “architectural” influences, which are paired with the influence of typical microstructural features. Lamellar metallic composites (LMCs) suit very well to systematically study these effects as layer size and arrangement can be easily varied.In this work, we prepared different Cu-based LMCs elucidate how heterostructured interfaces contribute to the overall materials properties. Microscopy methods like SEM and TEM were used to identify microstructural features as mechanical tests like tensile, microyielding and nanoindentation give insights into material properties on different length scales. It turned out, that the existence of dislocation networks at the interfaces play a dominant role at the transition from a Hall-Petch to the confined-layer-slip governed regime.
2:50 PM
Local Structural Ordering Affects the Toughening Ability of Amorphous Grain Boundary Complexions: Pulkit Garg1; Timothy Rupert1; 1University of California, Irvine
Amorphous grain boundary complexions act as toughening features within a microstructure as they can alter both crack nucleation and crack growth by efficiently absorbing dislocations. In this talk, we hypothesize that the toughening ability of complexions is determined by their local structural order and test this idea using atomistic simulations in Cu-Zr bicrystals. The structural order at amorphous-crystalline interfaces is found to be inversely related to incompatibility between the two confining grains, meaning that large incompatibilities between the confining crystals lead to a less ordered amorphous-crystalline interface regions. The variations in local structural ordering of amorphous-crystalline interfaces alter their interactions with the plastic strain brought by the incoming dislocations, with some amorphous complexions being more resistant to crack nucleation and growth as compared to the others. Thus, the entire grain-complexion-grain system must be considered to understand the toughening abilities of complexions and design nanocrystalline alloys with improved ductility and strength.
3:10 PM Invited
Mesoscale Model for Stress Field Evolution at Grain Boundaries Motivated by Atomistic Simulations of Dislocation-Grain Boundary Interactions: Darshan Bamney1; Royce Reyes2; Laurent Capolungo1; Douglas Spearot2; 1Los Alamos National Laboratory; 2University of Florida
Discrete dislocation dynamics (DDD) is a mesoscale modeling technique that simulates the dynamics and interactions of dislocations. Unfortunately, the utility of DDD simulations for problems that involve grain boundaries (GBs) is compromised by missing defect physics. The objective of this work is to use molecular dynamics (MD) simulations to study the interaction between an expanding dislocation loop and a grain boundary. The GBs chosen have stress fields that can be captured via an array of wedge disclination dipoles. Interaction details are examined via a new implementation of the atomic Nye Tensor, revealing that absorbed dislocation content is deposited along the wedge disclination dipoles. Motivated by these MD results, a mesoscale model for the evolution of a GB stress field due to dislocation – grain boundary interactions is developed. DDD simulations reveal that accumulated dislocation content from prior slip transmission lowers the external driving stresses required for subsequent slip transmission.
3:40 PM Break
4:00 PM Cancelled
Modeling Interfaces in Strain Gradient Plasticity: Miroslav Zecevic1; Aritra Chakraborty1; Ricardo Lebensohn1; Laurent Capolungo1; 1Los Alamos National Laboratory
In most strain gradient plasticity formulations, interfaces between different phases (or grains) are assumed either completely free (micro-free), or completely impenetrable (micro-hard) to dislocation flow. However, experiments and discrete dislocation dynamics simulations indicate that the interface behavior is far more complex. We formulate a novel interfacial constitutive relations, motivated by discrete dislocation dynamics simulations. In the proposed model, dislocations are allowed to flow through, and to accumulate in the interfaces. Expressions for interface resistance to dislocation flow and accumulation are derived using thermodynamic relations. The proposed interfacial constitutive relations are implemented within strain gradient crystal plasticity micromechanical model, based on Fast Fourier Transforms. Predictions of the model are compared with discrete dislocation dynamics simulations. In addition, model is applied to simulate behavior of nano-metallic laminate under layer parallel compression.
4:20 PM
Dislocation Transmission across 3D Interfaces in Cu/Nb Nanolaminates: Shuozhi Xu1; Justin Cheng2; Mauricio Leo2; Nathan Mara2; Irene Beyerlein3; 1University of Oklahoma; 2University of Minnesota, Twin Cities; 3University of California, Santa Barbara
In metallic systems, 3D interfaces are heterophase interfaces with nanoscale thickness and contain the chemical elements of the two adjacent crystals, from which the interfaces can be chemically and/or structurally distinct. Unlike 2D sharp interfaces across which the material properties change abruptly, the 3D interfaces provide a smoother intergranular transition in material properties. Numerical approaches for materials containing 3D interfaces need to account for multiple phases, which is challenging. Here, we advance a phase-field dislocation dynamics (PFDD) model to treat materials consisting of phases differing in composition, structural order, and size in the same system. In this model, the heterogeneities with a general geometry and plastic deformation on slip planes progress hand in hand. We then apply PFDD to studying the transmission of dislocations across 3D interfaces in Cu/Nb nanolaminates. Selected simulation results are compared against experiments. Origins of the enhancement in strength and plasticity in the nanolaminates are discussed.
4:40 PM
Effect of Interfacial Structure on Mechanical Behavior of Nanolayered Ti/TiN Composites: Ashlie Hamilton1; Justin Cheng1; Mauricio De Leo1; Kevin Baldwin2; Nathan Mara1; 1University of Minnesota - Twin Cities; 2Los Alamos National Laboratory
Metal-Ceramic Composites have been used to enhance the performance of materials by combining the benefits of high hardness from the ceramic layer and ductility of the metallic layer. Our recent work revealed that chemical and structural gradients over nanometer length scales simultaneously enhance the strength and deformability of nanolayered composites. However, this work has been limited to metallic systems. In this study, multilayer Ti/TiN composites containing either chemically abrupt interfaces, or a nitrogen gradient were deposited via magnetron sputtering. Spherical and Berkovich nanoindentation determines hardness, modulus, and indentation stress-strain behavior as a function of layer thickness and interface structure. Transmission Electron Microscopy reveals a gradient in structure over nanometers to tens of nanometers between the hexagonal-close-packed pure titanium phase, and the NaCl-type structure of TiN. We discuss strengthening effects in terms of the interplay between layer thickness, atomic interfacial structure and chemistry, and dislocation-based mechanisms.