Local Ordering in Materials and Its Impacts on Mechanical Behaviors, Radiation Damage, and Corrosion : Session V
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
Wednesday 8:30 AM
March 22, 2023
Room: Sapphire 411A
Location: Hilton
Session Chair: Blas Uberuaga, Los Alamos National Laboratory; Xiaoqing Pan, University of California, Irvine; Yang Yang, The Pennsylvania State University; Penghui Cao, University of California, Irvine
8:30 AM Invited
Direct Observation of Local Ordering and Charge Distribution in High Entropy Oxides: Lei Su1; Huaixun Huyan1; Abhishek Sarkar2; Wenpei Gao1; Xingxu Yan1; Christopher Addiego1; Robert Kruk2; Horst Hahn2; Xiaoqing Pan1; 1University of California Irvine; 2Karlsruhe Institute of Technology
The enhanced compositional flexibility to incorporate multiple-principal cations in high entropy oxides (HEOs) offers the opportunity to expand boundaries for accessible compositions and unconventional properties in oxides. Attractive functionalities have been reported in some bulk HEOs, which are attributed to the long-range compositional homogeneity, lattice distortion, and local chemical bonding characteristics in materials. However, the intricate details of local composition fluctuation, metal-oxygen bond distortion and covalency are difficult to visualize experimentally, especially on the atomic scale. Here, we present the atomic structure-chemical bonding-property correlations in a series of perovskite-HEOs utilizing the recently developed four-dimensional scanning transmission electron microscopy techniques which enables to determine the structure, chemical bonding, electric field, and charge density on the atomic scale. The existence of compositional fluctuations along with significant composition-dependent distortion of metal-oxygen bonds is observed. Consequently, distinct variations of metal-oxygen bonding covalency are shown by the real-space charge-density distribution maps with sub-Å resolution.
9:00 AM Invited
Characterizing Local Order in Disordered Materials: Shuoyuan Huang1; Carter Francis1; Paul Voyles1; 1University of Wisconsin
Discerning local order in disordered materials poses a substantial challenge in materials science. In experiments, electron nanodiffraction in the form of 4D STEM is a useful tool. A nanometer-diameter electron probe can obtain diffraction from as one hundred atoms, which is sensitive to ordered structures in glasses and orientation and strain in crystals. STEM scanning can produce spatial maps of these quantities. We have developed a new method to identify rotational symmetries in electron nanodiffraction patterns from metallic glasses with reduced artifacts compared to previous approaches. The degree of rotational symmetry and the density of symmetric structures in the glass is correlated to the glass thermal stability and hardness. We have also developed methods generalized from 2D image processing into 4D to find “important” features in large, complex, 4D STEM data sets. These features can be used to find strongly diffracting clusters in glasses or for orientation imaging in crystals.
9:30 AM Invited
Chemical and Structural Disorder for Tuning Properties of Materials: Horst Hahn1; 1Karlsruhe Institute of Technology
Many properties of crystalline and amorphous materials can be modified by the local structure and chemistry. Examples are local ordering in high entropy materials, defect ordering in intermetallic compounds, interfaces in crystalline and amorphous nanomaterials, and structural modifications in shear bands of metallic glasses. The control of the local ordering allows the tuning of properties of materials, however, requires detailed characterization of the local environment and elemental distribution at the atomic scale using advanced methods. The talk will address several of the ordering effects mentioned above and correlate the ordering with mechanical properties, atomic diffusion, radiation resistance, etc. in nanocrystalline materials, nanoglasses and high entropy alloys.
10:00 AM Break
10:15 AM Invited
Disorder and Transport in Irradiated Complex Oxides: Blas Uberuaga1; 1Los Alamos National Laboratory
Disorder is a natural consequence of irradiation in complex oxides. So is the formation of defects. These two phenomena are intricately linked, with disorder impacting transport and transport evolving disorder. However, the relationship between the two isn’t yet established. Here, we describe integrated computational and experimental studies that provide insight into the coupling between disorder and defect transport in complex oxides such as pyrochlore, spinel, and perovskite. We show that cation disorder has a direct and significant impact on transport while cation transport leads to cation reordering. We further show how cation disorder is not homogeneous across a material, but varies spatially with microstructure. We finally show that both the crystal chemistry and structure impact the coupling between disorder and transport, providing insight into how disorder in these materials impact evolution under extreme environments such as irradiation and corrosion.
10:45 AM Invited
Long- and Short-range Ordering versus Disordering in Compositionally Complex Fluorite-based Oxides: Jian Luo1; 1University of California, San Diego
This talk will review our recent work on investigating long- and short-range orders and order-disorder transitions (ODTs) in compositionally complex fluorite-based oxides (CCFBOs). In 2018, we first reported the YSZ-like high-entropy fluorite oxides [JECS 2018]. Subsequently, we fabricated a series of medium- and high-entropy (ordered) pyrochlore oxides and showed that size disorder controls reduced thermal conductivity [Scripta 2020]. We further proposed to extend “high-entropy ceramics (HECs)” to "compositionally complex ceramics (CCCs)" [JECS 2020; JMS 2020] to include non-equimolar compositions and short- and long-range ordering that reduce configurational entropies but offer additional dimensions to tailor and improve properties. We discovered composition-induced [Acta 2021] and redox-induced [Scripta 2022] pyrochlore-fluorite ODTs in 10- and 11-compomnent CCFBOs. We showed the short-range weberite ordering cause ultralow thermal conductivity [Acta 2022]. We discovered ultrahigh-entropy weberite and fergusonite phases and a pyrochlore–weberite transition in 21-component CCFBOs [JAC 2022]. On-going (unpublished) results will also be discussed.
11:15 AM
Short Range Order in Disordered Spinel and the Impact on Cation Vacancy Transport: Peter Hatton1; Blas Uberuaga1; 1Los Alamos National Lab
Spinels are important complex oxides for use in radiation damage environments and resulting from the corrosion of steels. It is known that, in these environments, normal spinels exist with some concentration of antisite cation pairs known as inversion. We use atomistic modeling to show that even in highly disordered states characterized by high levels of inversion, spinel still shows some short-range order that manifests itself in antisite chains. The propensity to form these antisite chains is confirmed through Monte Carlo simulations in FeCr2O4, NiCr2O4 and MgAl2O4. We consider the effect of antisite chains on the diffusivity of cation vacancies and find the effect strongly depends on the spinel chemistry. At the extremes, chains significantly increase or drastically decrease vacancy transport depending on spinel chemistry. These dramatically different effects are explained by the assessment of the thermodynamic stability of the antisite chains and contrasting attractive/repulsive interactions of vacancies with the chains.
11:35 AM Invited
Molten Salt Corrosion of Ni-20Cr Model Alloy: Lingfeng He1; Kaustubh Bawane2; Xiaoyang Liu3; Fei Teng2; Weiyue Zhou4; Laura Hawkins2; Trishelle Copeland-Jonson2; Yachun Wang2; Michael Woods2; Ruchi Gakhar2; Daniel Murray2; Phillip Halstenberg5; Karen Chen-Wiegart3; Shannon Mahurin5; Sheng Dai5; Michael Short4; Lin Shao6; Simon Pimblott2; James Wishart7; 1North Carolina State University; 2Idaho National Laboratory; 3Stony Brook University; 4Massachusetts Institute of Technology; 5Oak Ridge National Laboratory; 6Texas A&M University; 7Brookhaven National Laboratory
Molten Salt Reactors (MSRs) are leading candidates for next-generation nuclear reactors contributing to the US energy supply. One of the most critical challenges in the fruition of MSRs is the corrosion of salt-facing structural materials. To comprehend the corrosion behavior of commercial alloys and develop a corrosion mitigation strategy in MSRs environment, it is of significance to reveal the microstructure and microchemistry of simple model alloys in corrosion, radiation, and stress extremes. In this work, electron backscatter diffraction and electron tomography in a focused ion beam system, transmission electron microscopy, and synchrotron X-ray nano-tomography techniques are used to characterize the microstructural evolution of Ni-20Cr model alloys corroded in molten salts as a function of time and temperature. The mechanical degradation due to grain boundary corrosion is evaluated by in-situ micro tensile testing. The corrosion-induced defects play a dominant role in the failure mode of grain boundaries under corrosion with/without radiation.