ICME 2023: Linkages: Microstructure I
Program Organizers: Charles Ward, AFRL/RXM; Heather Murdoch, U.S. Army Research Laboratory

Tuesday 3:00 PM
May 23, 2023
Room: Caribbean VI & VII
Location: Caribe Royale

Session Chair: Michael Tonks, University of Florida

3:00 PM
Simulations Showing the Formation of Grooves and Ledges Over γ' Precipitates During High-temperature Creep: A Dynamically Coupled Discrete Dislocation Dynamics and Phase-field Model: Tushar Jogi¹; Markus Stricker¹; ¹Ruhr-University Bochum
     Superalloys derive their superior high-temperature strength via interactions between ordered γ′ precipitates and matrix dislocations. However, during creep deformation or cooling from service temperatures, γ/γ′ interfaces (GI) often show irregularities, which can severely deteriorate the high-temperature strength of superalloys. For example, Parsa et al. (Acta Mater., 2015) reported the formation of ledges and grooves (LG) over γ′ precipitates after the cooling of crept samples. Experiments fail to explain the formation of these irregularities as only the final state can be assessed. Hence, we present a coupled framework that accounts for the dynamic interaction between dislocations and moving GI and their simultaneous co-evolution. We employ an appropriate coarse-graining approach to account for the influence of the dislocations on the dynamics of GI and decoupled the glide and climb of dislocation through a time-scale separation scheme. Using this framework, we show the mechanisms resulting in the formation of LG at the GI.

3:20 PM
Phase Field Modeling Investigation of Polycrystalline Grain Growth Using a Spherical-Gaussian-based 5-D Computational Approach: Lenissongui Yeo¹; Michael Costa¹; Jacob Bair¹; ¹Oklahoma State University
    Spherical gaussians, allowing the modeling of complex anisotropies, are used in modeling anisotropic polycrystalline grain growth (GG). Quaternions, assigned to individual grains as orientations and as misorientations for grain boundaries, conduct the ongoing mesoscale changes. A 5-D space scanning generates meaningful grain boundaries; inputted into the continuous function developed by Bulatov et al. to calculate grain boundary energy (GBE); which local minimas are used in the phase field model. The methodology involves using 2-D gaussian switches, which match the misorientation between grains with misorientations for the GBE minima. Accounting a threshold range for the minimas, the switch activates a Spherical Gaussian to set the GBE to the desired value; creating in combination a full 5-D GBE space. Multiphysics Object Oriented Simulation Environment (MOOSE), where reduced order parameters still retain individual grain identification useful for individually assigned quaternions, is used for implementation; with validation performed through bicrystal simulations of known outcomes.

3:40 PM
Unravelling the Ultrahigh Modulus of Resilience of Core-Shell SU-8 Nanocomposite Nanopillars Fabricated by Vapor-Phase Infiltration: Ying Li¹; ¹University of Wisconsin-Madison
    We fabricated core-shell SU-8 nanocomposite nanopillars via vapor-phase infiltration of nanoscale amorphous aluminum oxides, into their 50 nm deep surface region and performed microstructural and nanomechanical characterization as well as analytical and atomistic modeling to gain a fundamental insight into the ultrahigh modulus of resilience exhibited by these nanocomposites, which are orders of magnitude higher than most high-strength engineering materials. The results of experimental and numerical studies show that the ultrahigh modulus of resilience of our core-shell nanocomposites results from: the low aspect ratio of amorphous aluminum oxide nano-particulates; the particulate size being comparable to or slightly larger than the free volume of the composite matrix; and the extremely thin aluminum oxide interconnecting links emanating from nano-particulates. These unique microstructural features produce the unusual combination of low Young’s modulus and high yield strength, leading to the exceptionally high modulus of resilience as well as its weak dependence on strain rate.

4:00 PM
Predicting the Metallurgical Bond at the Interface Between Two Aluminum Sheets Joined Using High-velocity Riveting Through Finite Element and Molecular Dynamics: Ayoub Soulami¹; Daniel Ramirez-Tamayo¹; Krishna Pitike¹; Lei Li¹; Benjamin Schuessler¹; Sridhar Niverty¹; Vineet Joshi¹; ¹Pacific Northwest National Laboratory
    High-Velocity Riveting (HVR) is a novel joining method that allows the joining of two sheets of metal through a metallurgical bond resulting from the high-speed impact with the rivet and the die. 3D finite element (FE) models were developed and used to help inform the die design and processing conditions. The model was able to simulate the joining process and inform the processing conditions. Additionally, outputs from the FE model are used as an input to a Molecular Dynamics (MD) model developed to investigate the atomistic mechanisms at nm to 痠 length scale that may influence the metallurgical bonding, such as inter-diffusion of atoms and local recrystallization of Aluminum at the interface. This ICME framework is suited to predict and understand the link between processing parameters and the physics of the bonding at the interface between the joined materials.