Lattice misorientation evolution and grain refinement in Al-Si alloys under high-strain shear deformation

Gwalani, Bharat; Fu, Wenkai; Olszta, M; Silverstein, Joshua; Yadav, Digvijay; Manimunda, Praveena; Guzman, Anthony D.; Xie, Kelvin; Rohatgi, Aashish; Mathaudhu, Suveen; Powell, Cynthia A.; Li, Yulan; Devaraj, Arun

doi:10.1016/j.mtla.2021.101146

Cited by 18 publications

(8 citation statements)

References 34 publications

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“…Because of deformation heterogeneity, each grid in the representative volume element (RVE) has its orientation in the current configuration, which causes kernel average misorientation (KAM). 32 Consider two grids, k and m. O k and O m are their orientation matrices, respectively. The misorientation angle Δψ k,m between grids k and m can be calculated by…”

Section: Methodsmentioning

confidence: 99%

Extended Shear Deformation of the Immiscible Cu–Nb Alloy Resulting in Nanostructuring and Oxygen Ingress with Enhancement in Mechanical Properties

Gwalani

Pang

et al. 2022

ACS Omega

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Deformation processing of immiscible systems is observed to disrupt thermodynamic equilibrium, often resulting in nonequilibrium microstructures. The microstructural changes including nanostructuring, hierarchical distribution of phases, localized solute supersaturation, and oxygen ingress result from high-strain extended deformation, causing a significant change in mechanical properties. Because of the dynamic evolution of the material under large strain shear load, a detailed understanding of the transformation pathway has not been established. Additionally, the influence of these microstructural changes on mechanical properties is also not well characterized. Here, an immiscible Cu-4 at. % Nb alloy is subjected to a high-strain shear deformation (∼200); the deformation-induced changes in the morphology, crystal structure, and composition of Cu and Nb phases as a function of total strain are characterized using transmission electron microscopy and atom probe tomography. Furthermore, a multimodal experiment-guided computational approach is used to depict the initiation of deformation by an increase in misorientation boundaries by crystal plasticity-based grain misorientation modeling (strain ∼0.6). Then, co-deformation and nanolamination of Cu and Nb are envisaged by a finite element method-based computational fluid dynamic model with strain ranging from 10 to 200. Finally, the experimentally observed amorphization of the severely sheared supersaturated Cu–Nb–O phase was validated using the first principle-based simulation using density functional theory while highlighting the influence of oxygen ingress during deformation. Furthermore, the nanocrystalline microstructure shows a >2-fold increase in hardness and compressive yield strength of the alloy, elucidating the potential of deformation processing to obtain high-strength low-alloyed metals. Our approach presents a step-by-step evolution of a microstructure in an immiscible alloy undergoing severe shear deformation, which is broadly applicable to materials processing based on friction stir, extrusion, rolling, and surface shear deformation under wear and can be directly applied to understanding material behavior during these processes.

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Section: Methodsmentioning

confidence: 99%

Extended Shear Deformation of the Immiscible Cu–Nb Alloy Resulting in Nanostructuring and Oxygen Ingress with Enhancement in Mechanical Properties

Gwalani

Pang

et al. 2022

ACS Omega

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“…Одним из преимуществ данного процесса является существенное измельчение зеренной структуры. В работе [Gwalani et al, 2021] для изучения механизмов и особенностей деформирования в указанном процессе предлагается теоретическое и экспериментальное исследование модельной задачи циклического сдвигового нагружения. Для моделирования использована прямая упруговязкопластическая модель (реализация в пакете DAMASK), в которой зерна в отсчетной конфигурации представляются совокупностью субзерен.…”

Section: многоуровневые модели ориентированные на описание дислокацио...unclassified

Evolution of the grain structure of metals and alloys under intense plastic deformation: multilevel models

Трусов

Ostanina

Shveykin

2022

PNRPU Mechanics Bulletin

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It is well known that the performance properties of products made of metals and alloys are determined mainly by the meso- and microstructure of the latter. The structure of materials is formed and undergoes significant changes in the processes of manufacturing parts and structures using thermomechanical processing methods. A very important parameter that determines the physical and mechanical characteristics of materials is the grain structure (size, shape, relative positions of grains and inclusions of various phases). In recent decades, in this regard, special attention has been paid to the processes of severe plastic deformation (SPD), which make it possible to obtain a submicro- and nanocrystalline grain structure, which provides a significant increase in the performance properties of products made of metals and alloys. The development of SPD technologies in modern conditions is unthinkable without mathematical modeling of the processes under consideration; the most important component in the development of such a "toolkit" are constitutive relations (or, more broadly, constitutive models). In connection with the foregoing, the latter should be able to describe the evolutionary structure at various scale levels. Until now, the practice of developers of materials processing technologies has been dominated by the use of macrophenomenological models based on classical continuum theories of plasticity, viscoplasticity, and creep. From the second half of the 20th century to the present, various improvements to the constitutive models of the above class have been proposed, in which additional parameters and kinetic equations are introduced for them, describing certain characteristics of the structure of materials. As a rule, such models make it possible to obtain an adequate picture of the changing structure, however, for specific materials and methods of thermomechanical treatment. At the same time, such models, unfortunately, do not have the necessary universality; when changing the material or processing method, they have to be significantly “customized” to specific conditions, up to a complete change in the relationships included in the model. A brief review of works devoted to the creation and application of models of this class is given in the previous article by the authors. The most promising and possessing a significant degree of universality, according to the authors, are currently multilevel constitutive models based on the introduction of internal variables and physical theories of plasticity (elastoviscoplasticity). A review of works that consider various aspects of the formulation, modification, numerical implementation and application of such models is proposed in this article. The main attention is paid to models focused on the description of changes in the structure of materials due to dislocation-disclination mechanisms; a brief note is given on models that take into account thermally activated diffusion mechanisms, due to which the processes of recovery and recrystallization are realized.

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“…Atoms at the bottom of the simulation cell in z-direction are fixed. The typical sliding speed of a tribometer test to emulate the SPP conditions in small material volumes is usually in the range of submeters to tens of meters per second [18,19,47,48]. Considering the short timescale of MD simulations as compared with experiments, a constant velocity of the rigid contact was set to be 300 m s −1 during both compressive and shear stages.…”

Section: Simulation Cell Setup and Approachesmentioning

confidence: 99%

“…Materials undergoing SPP, such as friction stir processing [8][9][10], shear-assisted processing and extrusion [11,12], and high-pressure torsion [13,14], are subjected to complex stress fields which are inhomogeneous and evolving in time due to lateral constraints, rough contact surfaces and friction. Experiments show that initial microstructure in the near-surface region can be significantly refined under SPP [12,[15][16][17][18][19]. For example, a pin-on-disk tribometer test [18,19] designed to study grain refinement mechanisms, found that the Al structure beneath the contact surface is refined from ∼100 μm to 10-100 nm size, i.e.…”

Section: Introductionmentioning

confidence: 99%

“…Experiments show that initial microstructure in the near-surface region can be significantly refined under SPP [12,[15][16][17][18][19]. For example, a pin-on-disk tribometer test [18,19] designed to study grain refinement mechanisms, found that the Al structure beneath the contact surface is refined from ∼100 μm to 10-100 nm size, i.e. the grain size is reduced by up to three orders of magnitude, after 5000 cycles of reciprocating shear deformation (see figure 1).…”

Section: Introductionmentioning

confidence: 99%

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Formation and dissociation of shear-induced high-energy dislocations: insight from molecular dynamics simulations

Chen¹,

Hu²,

Gwalani³

et al. 2022

Modelling Simul. Mater. Sci. Eng.

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Solid-phase processing (SPP) allows one to create complex microstructures, not achievable via thermal processing alone. The resulting structures exhibit a rich palette of defects, both thermal and non-thermal, including defect substructures, such as dislocation networks. It is essential to understand the mechanisms of deformation and defect structure formation to guide SPP towards achieving desired microstructures and material properties. In this study, large-scale molecular dynamics simulations are used to investigate the effects of inhomogeneous strain distribution, that mimics deformation conditions of tribological tests, on the evolution of defects under severe shear deformation in polycrystalline Al. Analysis of defect nucleation and reaction pathways reveals that strong geometric constraints suppress the nucleation and slide of low energy dislocation 1/2<110>{111} but promote the nucleation and slide of high energy dislocations, such as [1-10](001) and 1/2[1-1-2](1-11). A rough contact surface, characteristic to tribological tests, imposes an inhomogeneous stress field leading to inhomogeneous defect substructures due to location-dependent activation of slip systems. The results suggest that high-energy dislocations can dominate the evolution of grain structures in highly constrained environments, which should be considered in modeling plastic deformation and grain refinement during SPP.

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Lattice misorientation evolution and grain refinement in Al-Si alloys under high-strain shear deformation

Cited by 18 publications

References 34 publications

Extended Shear Deformation of the Immiscible Cu–Nb Alloy Resulting in Nanostructuring and Oxygen Ingress with Enhancement in Mechanical Properties

Extended Shear Deformation of the Immiscible Cu–Nb Alloy Resulting in Nanostructuring and Oxygen Ingress with Enhancement in Mechanical Properties

Evolution of the grain structure of metals and alloys under intense plastic deformation: multilevel models

Formation and dissociation of shear-induced high-energy dislocations: insight from molecular dynamics simulations

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