Local Ordering in Materials and Its Impacts on Mechanical Behaviors, Radiation Damage, and Corrosion : Session VI
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 2:00 PM
March 22, 2023
Room: Sapphire 411A
Location: Hilton
Session Chair: Fadi Abdeljawad, Clemson University; Daniel Gianola, University of California, Santa Barbara
2:00 PM Invited
Tunable Short-range Order Within Amorphous Complexions and Its Connection to Damage Nucleation: Pulkit Garg1; Esther Hessong1; Tianjiao Lei1; Timothy Rupert1; 1University of California, Irvine
Grain boundaries are common sites for damage nucleation during plastic formation, especially in nanocrystalline metals. In this talk, we explore how structural short-range order determines damage tolerance in disordered complexions. The incompatibility between grains is first shown to determine the level of order/disorder at the amorphous-crystalline interface, with the grain-film-grain system finding a local equilibrium configuration. The amorphous-crystalline interface is critical to damage tolerance because it is the location where incoming dislocations must be accommodated, with subsequent atomistic modeling showing that damage nucleation and short-range order are intimately related in this region. These theoretical insights are then leveraged to produce nanocrystalline alloys with complex interfacial chemistries and tunable structural short-range order, opening pathways for design of tough nanostructured metals.
2:30 PM
Chemical and Structural Ordering in Amorphous Complexions Determines the Plasticity of Nanocrystalline Cu Alloys: Esther Hessong1; Tianjiao Lei1; Mingjie Xu1; Timothy Rupert1; 1University of California, Irvine
Amorphous complexions are important microstructural features because they increase the toughness of the grain boundary region. Chemical segregation behavior in amorphous complexions of nanocrystalline Cu-rich alloys was investigated using high-resolution transmission electron microscopy. Dopant segregation behavior varied across complexions, where the dopants with favorable glass-forming ability were more concentrated in the center of the complexion, and dopants with less favorable-glass forming ability were more concentrated along the amorphous-crystalline interface. Additionally, nanobeam electron diffraction was used to obtain diffraction patterns across complexions at each real space pixel location, to compare the structure of the abutting crystals, amorphous-crystalline interfaces, and amorphous interior. The diffraction patterns of the local regions were correlated with differently oriented polyhedra, thus quantifying the short-range order across the grain boundaries. To determine the effects of the localized chemical and structural ordering, mechanical testing was performed on different length scales, including both in-situ micropillar compression and bulk compression tests.
2:50 PM Invited
Non-monotonic Role of Chemical Heterogeneity on Interfacial Crack Growth in Fe-Ni-Cr Alloys: Yue Fan1; 1University of Michigan
Propagations of micro-cracks at grain boundaries (GBs) are investigated in a generic Fe-Ni-Cr model. While keeping all other parameters the same (e.g. crystallography, size, thermo-mechanical stimuli), we control the local chemical orders at GBs via Metropolis Monte Carlo algorithm and then compare the growth of a pre-existing nano-void under cyclic loading in the context of low cycle fatigue. It is found the crack propagates fastest at intermediate level of chemical heterogeneity. In addition, the crack growth is not continuous but instead follows an intermittent pattern, and the abrupt crack advances are driven by the spatial density of those atoms with extreme compressive residue stresses. By examining more general interfaces without pre-existing singularities/cracks, we demonstrate the atomic-level stress variations are non-affine in nature, and the magnitude of non-affine fluctuations also maximizes at intermediate chemical orders. These findings may provide a new perspective towards the understanding of intermediate temperature ductility loss phenomenon.
3:20 PM
Grain Boundary Segregation in Polycrystals: Isotherms, Computation, and Data Science: Malik Wagih1; Christopher Schuh1; 1Massachusetts Institute of Technology
Solute segregation at grain boundaries (GBs) strongly impacts, among others, the corrosion resistance and mechanical properties of metallic alloys. The local atomic environment of a GB site determines how well it can accommodate a solute atom, which can range from being repulsive to strongly attractive. It is therefore important to have a thorough understanding of the vast range of local atomic environments at the GB network in order to be able to control and design for solute segregation in polycrystalline alloys. In this talk, we will review our recent work to develop thermodynamic, computational, and data science frameworks to rigorously understand this phenomenon at the atomistic scale, and to develop comprehensive segregation databases for hundreds of substitutional alloys. We will also discuss how we are extending these frameworks to address the challenging problem of interstitial segregation.
3:40 PM Break
3:55 PM Invited
Engineering the Extent of Grain Boundary Ordering via Pre-melting in Nanocrystalline Al Alloys: Jungho Shin1; Tianjiao Lei2; Hannah Howard1; Glenn Balbus3; Timothy Rupert2; Daniel Gianola1; 1University of California-Santa Barbara; 2University of California Irvine; 3Air Force Research Laboratory
Segregation-engineered nanocrystalline alloys with chemically enriched grain boundaries enable combinations of exceptional mechanical behavior and thermal stability. With judicious alloying and processing choices, these materials can also host amorphous complexions that are intrinsically stable at elevated temperatures when the disordered nanoscale interface zone can exist in equilibrium with its crystalline abutting neighbors. In this work, we demonstrate synthesis and processing routes for controlling disorder at the interfaces within segregation-engineered nanocrystalline aluminum alloys. We demonstrate that exceptional thermal stability and mechanical strength arises in several ternary aluminum alloys by promoting grain boundary pre-melting events at sub-solidus temperatures followed by subsequent cooling to the glassy state. Ultrafast differential scanning nanocalorimetry combined with electron microscopy reveals the role of cooling rate on the solidification products from the interface liquid, and a path-independence of the subsequent disordering temperatures. Finally, we discuss the implications of these disorder-engineered alloys for bulk processability with low energy budget.
4:25 PM
The Effects of Local Order in Molten Metals on Glass Formation: Doğuhan Sarıtürk1; Can Okuyucu1; Yunus Kalay1; 1Middle East Technical University
Partial devitrification of the Al-RE marginal metallic glasses results in an anomalous nucleation rate of nanocrystals embedded in an amorphous matrix. An exact explanation for the mechanism underlying the formation of highly populated nanocrystals is still missing. We previously investigated the as-quenched structure in detail and found that some medium-range order (MRO) clustering is responsible for the nanocrystallization of fcc-Al after devitrification. In this study, we investigated the local order in liquid by the use of MD simulations with EAM potential to reveal the structural evolution in molten Al-RE (RE: Sm, Tb) within their glass formation range. We found that the MRO observed in the as-quenched structure originated from the molten state which controls the glass formation in marginal metallic glass formation. The corresponding change in viscosity and its effect on the formation of local ordering in liquid were investigated by Green-Kubo Viscosity and cluster analyses, respectively.
4:45 PM
Preferential Precipitation on Annealing Twin Boundaries and Its Effect on Strain Localization: Semanti Mukhopadhyay1; Chaitali Patil1; Hariharan Sriram1; You Rao2; Longsheng Feng3; Maryam Ghazisaeidi1; Stephen Niezgoda1; Yunzhi Wang1; Michael Mills1; 1The Ohio State University; 2EPFL; 3Lawrence Livermore National Laboratory
Annealing twin boundaries (ATBs) in superalloys are vulnerable sites for strain localization and subsequent failure. However, despite several attempts, the role of precipitate-ATB interactions on strain localization in superalloys remains unclear. Thus, we studied γ’ precipitate evolution along ATBs and consequent mechanical behavior in several superalloys. The present work investigates how various factors contribute to the well-documented strain localization events. For this purpose, we complement results from In-Situ tensile tests with full-field crystal plasticity simulations. Preliminary results indicate that several superalloys exhibit preferential precipitation of γ’ or γ’’ on the ATBs. In this case, local phase transformations at the boundaries influence heterogeneous nucleation on the ATBs. This preferential precipitation also appears to create precipitate-free zones parallel to ATBs, which could exacerbate strain localization. Finally, we will discuss strategies to avoid such intense strain localization events near ATBs based on our analyses.
5:15 PM Invited
Coupled Grain Boundary and Twin Boundary Deformation in Metallic Materials: Jiangwei Wang1; Qi Zhu2; Haofei Zhou1; Xianghai An3; 1Zhejiang University; 2Nanyang Technological University; 3The University of Sydney
Polycrystalline and nanocrystalline metallic materials often show interface-dominated plasticity, where the coupling between neighboring interfaces plays important role, especially during the dynamic process of deformation. This talk presents the recent progresses of coupled grain boundary (GB) and twin boundary (TB) deformation in metallic materials. GB-emitted nanotwin was found effectively to tune the deformability of its source GB, favoring the GB-dominated process; while, the large kinks on defective TBs can be regarded as small GB segment, which can facilitate the formation of secondary nanotwins. Such self-activated twin multiplication process acts as a built-in source for hierarchical twin, which develops gradually and induces the formation of five-fold nanotwin and nanotwin network eventually. The coupled GB-TB deformation critically controls the dynamic microstructural evolution during the deformation of metallic materials with low stacking fault energy, as demonstrated by the complicated GB-TB networks in a variety of deformed nanocrystalline materials.