Local Ordering in Materials and Its Impacts on Mechanical Behaviors, Radiation Damage, and Corrosion : Session III
Sponsored by: TMS Structural Materials Division, TMS: Chemistry and Physics of Materials Committee, TMS: Nuclear Materials Committee, TMS: Corrosion and Environmental Effects Committee
Program Organizers: Penghui Cao, University of California, Irvine; Yang Yang, Pennsylvania State University; Fadi Abdeljawad, Lehigh University; Irene Beyerlein, University of California, Santa Barbara; Enrique Lavernia, University of California, Irvine; Robert Ritchie, University of California, Berkeley

Tuesday 8:00 AM
March 21, 2023
Room: Sapphire 411A
Location: Hilton

Session Chair: Robert Ritchie, University of California, Berkeley; Penghui Cao, University of California, Irvine; Yang Yang, The Pennsylvania State University; Irene Beyerlein, University of California, Santa Barbara


8:00 AM  Invited
Different Scales of Chemical and Structural Ordering in Advanced High Strength Steels: Dierk Raabe1; Dirk Ponge1; Binhan Sun1; 1Max-Planck Institute
     Structural and chemical ordering phenomena across multiple length scales are typical characteristics of a number of advanced high-strength steels. They include features such as short and medium-range chemical ordering; highly ordered nanoprecipitate patterns; coupled mesoscopic chemical-structural ordering effects that can come from kinetic freezing, from the chemical decoration of lattice defects in part in conjunction with locally confined phase transformation effects and/or from chemical container phases that can be driven into a partial dissolution state that can trigger local phase transformations.These ordering features have been realised in a number of medium and high manganese steels, often with lean chemical bulk composition. These hierarchical ordering effects that involve different chemical and structural features across several length scales can be used to design a complex strain hardening behaviour and can even help to enhance the materials’ resistance to hydrogen embrittlement.

8:30 AM  
In-situ TEM Study of the Role of Short-range-order in the Deformation of Medium Entropy Alloy: Yang Yang1; Ying Han1; Yongwen Sun1; Mark Asta2; Robert Ritchie2; Andrew Minor2; 1The Pennsylvania State University; 2Lawrence Berkeley National Laboratory
    Several recent researches have shown strong evidence of chemically short-range-order (SRO) in medium/high-entropy alloys. While it is hypothesized that SRO can be another dimension to modulate the properties of structural materials significantly, much needs to be done to elucidate further how SRO impacts the materials' performance and the underlying mechanisms. Here, we perform in situ TEM mechanical testing and four-dimensional scanning transmission electron microscopy (4D-STEM) to reveal the evolution of SRO and its interaction with other defects in medium entropy alloy under deformation. The challenges and opportunities in the characterization of the dynamical behaviors of SRO will be discussed.

8:50 AM  Invited
Short-range Order Effects on Dislocation Mobilities in High-entropy Alloys from Atomistic Simulations: Sheng Yin1; Anas Abu-Odeh2; David Olmsted2; Jun Ding3; Wenqing Wang2; Flynn Walsh2; Robert Ritchie1; Mark Asta2; 1Lawrence Berkeley National Laboraory; 2University of California, Berkeley; 3Xi'an Jiaotong University
    We present results of atomistic simulations for core structures and mobilities of edge and screw dislocations in refractory high-entropy alloys. The work focuses specifically on understanding of the role of chemical short range order (SRO) on the energy landscapes and resulting dislocation mobilities. We present results for the MoNbTaW system (and its subsystems), which displays excellent high-temperature strength but poor tensile ductility. The mobility of edge dislocations is found to be enhanced by the presence of SRO, while the rate of double-kink nucleation in the motion of screw dislocations is reduced. The results are discussed in the context of known behavior in elemental bcc refractory metals, and binary concentrated solid solutions. They are also discussed in the context of anisotropy of dislocation mobility, which has been suggested as a key contributing factor of intrinsic ductility. Research supported by the DOE-BES Damage Tolerance in Structural Materials program.

9:20 AM Break

9:40 AM  Invited
Local Phase Transformations Associated with Extended Defects in Ni-base Superalloys: Michael Mills1; Ashton Egan1; Semanti Mukhopadhyay1; Steven Niezgoda1; Maryam Ghazisaeidi1; Emmanuelle Marquis2; Fei Xue2; Yunzhi Wang1; Tim Smith3; 1Ohio State University; 2University of Michigan; 3NASA Glenn Research Center
    Polycrystalline Ni-based superalloys are vital materials for disks in the hot section of aerospace and land-based turbine engines due to their exceptional microstructural stability and strength at high temperatures. In order to increase operating temperatures and hold times in these engines, hence increasing engine efficiency and reduction of carbon emissions, creep properties of these alloys becomes increasingly important. Microtwinning and stacking fault shearing through the strengthening γ’ precipitates are important operative mechanisms in the critical 600-800°C temperature range. Atomic-scale chemical and structural analyses indicate that local phase transformations (LPT) occur commonly during creep of superalloys. Furthermore, the important deformation modes can be modulated by LPT formation, enabling a new path for improving high temperature properties. This work is part of a GOALI-DMREF program funded by the National Science Foundation.

10:10 AM  
Diffusion Kinetics and Formation of Chemical Short-range Order in Alloys: Bin Xing1; Penghui Cao1; 1University of California, Irvine
    It is known that chemical short-range order (SRO) has impacts on various material behaviors, including mechanical deformation, radiation tolerance. In simulations, chemical SRO is typically generated from the hybrid Monte Carlo and molecular dynamics (MCMD) method, which merely considers system energy change associated with random atom swapping. Here, we aim to propose an alternative approach, which combines deep learning technique and kinetic Monte Carlo (KMC) method, to study SRO formation mediated by diffusion kinetics. It is shown that the proposed deep learning model can efficiently predict diffusion barriers in any local chemical configuration. With the energy barriers, atomic diffusion and the resulting SRO nucleation and growth are achieved using KMC. We expect that the chemical SRO generated from diffusion is different from that produced by the hybrid MCMD method. Meanwhile, KMC provides the diffusion timescale, which is helpful in evaluating the time needed for various degrees of chemical SRO formation.

10:30 AM  Invited
Integrating In Situ Experiment and Atomistic Modeling to Decipher Grain Boundary Deformation Mechanisms: Ting Zhu1; 1Georgia Institute of Technology
    With recent advances in atomistic modeling and in situ experimental technologies, there have been increased efforts to combine these approaches to understand atomic-scale deformation mechanisms at grain boundaries (GBs). In this talk, I will present recent studies that integrate in situ electron microscopy, nanomechanical testing, and atomistic modeling to investigate GB deformation mechanisms. We have combined in situ high resolution transmission electron microscopy experiments and atomistic simulations to unravel the atomic-scale processes of stress-driven GB sliding and structural transformation that occur unexpectedly at room temperature. We have also combined in situ MEMS-based nanomechanical testing and atomistic reaction pathway simulations to uncover the rate-controlling GB processes that dictate experimentally measured activation volumes in nanocrystalline metals. The ability to resolve the atomic-scale dynamic processes of GB deformation, through coupled in situ experiment and atomistic modeling, enables deep understanding of how GBs affect the plastic behavior of polycrystalline materials.

11:00 AM  
Mean-field Prediction of Short-range Ordering/Clustering Kinetics in Binary FCC Solid Solution Alloys: Anas Abu-Odeh1; Blas Uberuaga2; Mark Asta1; 1University of California Berkeley; 2Los Alamos National Laboratory
    The presence of short-range ordering (SRO) or clustering (SRC) in concentrated solid solution alloys has been shown to affect their mechanical properties. However, it is uncertain how long of an annealing time is required to reach an equilibrium SRO/SRC state. Being able to predict this facilitates the design of experiments dependent on SRO/SRC and provides the time dependence of properties that are a function of SRO/SRC. Kinetic Monte Carlo (kMC) simulations provide an avenue for these predictions but are dependent on parameterizing vacancy transition state energies which can be computationally expensive to calculate. We present comparisons of SRO/SRC kinetics in model FCC binary solid solutions obtained from kMC as well as a mean-field method (MFM). The MFM predicts relaxation kinetics that are typically within an order of magnitude of those obtained from kMC. The MFM requires much simpler inputs than kMC and can be extended to multicomponent systems.