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Strain pattern obtained after simulation of a system of size 256 × 256 to an average strain of 20b √ ρ (slip direction from left to right); greyscale: local strain in units of b √ ρ
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Context 1
... yields strongly anisotropic, striated strain patterns ( Figure 5) with strong correlations in the x direction (the direction of the slip plane) but weak correlations in the normal direction. This can be readily understood by looking at the elastic interactions in Fourier space: The Fourier transform of the elastic kernel is zero along the k x and k y directions, see Eq. (3.2). ...
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... it can by definition not tell anything about the spatial organization of slip. The formation of 'slip lines' as shown in Figure 5 hinges on the second-order gradient term in Eq. (3.3), which scales in Fourier space like k 2 γ( k) and is, hence, on large scales irrelevant in comparison with the long range elastic term, Eq. (3.2). However, the second-order gradient term has a decisive influence on the small-scale morphology of the deformation patterns, as it breaks the symmetry existing in the kernel in Eq. 3.1 between the x and y directions, and suppresses deformation heterogeneities in the direction of dislocation glide. ...
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Citations
... , and avalanche duration , from mechanical tests, acoustic emission (AE), and calorimetric results. Several analytical and numerical models have been developed to describe and predict the scaling behavior, for instance, discrete dislocation-dynamics (DDD) models [332][333][334][335][336][337][338][339], mean-field avalanche model [340][341][342], pinning-depinning models [343], and phase-field-crystal models [344]. Many of them are originally proposed for crystalline or polycrystalline materials, and focus on dislocation behavior. ...
Serrations and noise behaviors in plastically deforming solids are related to avalanches of deformation processes. In the stress-strain curves, the serrations characteristics are visible as stress drops or strain jumps. In fact, similar serration characteristics are ubiquitous in many structural and functional materials, such as amorphous materials [also metallic glasses, or bulk metallic glasses (BMGs)], high-entropy alloys (HEAs), superalloys, ordered intermetallics, shape-memory alloys (SMAs), electrochemical noise, carbon steels, twinning-induced plasticity steels (TWIP steels), phase-transformation-induced plasticity steels (TRIP steels), Al-Mg alloys, nano-materials, magnetic functional materials, and so on. Because of their unique and universal properties, many researchers have focused on this field to find out what causes the serration behaviors and what can be learned about the material from the serration characteristics. For example, the serration characteristics contain information about the mechanisms of plastic deformation and the structural evolution during deformation. However, due to many factors affecting the serration behavior and some uncertain or uncontrolled factors, it’s a difficult task to give a unified picture of a vast amount of serration data. This review article summarizes the results of previous studies in this rapidly-developing field, attempting to provide a new perspective in expounding the connection between macroscopic properties and micro-mechanisms.
... Many experiments on crystalline and amorphous plasticity can be fit using a value τ ∼ 3/2 (144). While older simulations seemed to agree with this value (145,146), newer simulations observe smaller values of τ ∼ 1.25 − 1.4 (147,148,15,149). 11 Mean field theories describe systems in high dimensions or with long-range forces. ...
We give a bird's-eye view of the plastic deformation of crystals aimed at the statistical physics community, and a broad introduction into the statistical theories of forced rigid systems aimed at the plasticity community. Memory effects in magnets, spin glasses, charge density waves, and dilute colloidal suspensions are discussed in relation to the onset of plastic yielding in crystals. Dislocation avalanches and complex dislocation tangles are discussed via a brief introduction to the renormalization group and scaling. Analogies to emergent scale invariance in fracture, jamming, coarsening, and a variety of depinning transitions are explored. Dislocation dynamics in crystals challenges non equilibrium statistical physics. Statistical physics provides both cautionary tales of subtle memory effects in nonequilibrium systems, and systematic tools designed to address complex scale-invariant behavior on multiple length and time scales.
... More recently the crackling noise during plastic deformation is being modeled. Simulations of slowly-sheared crystals using discrete dislocation-dynamics models [162,[194][195][196][197][198][199][200], continuum models [194], phase-field models [201], and phase field crystal models [202] all reveal a broad (power-law) distributions of the serration sizes in the associated stress-strain curves. ...
... More recently the crackling noise during plastic deformation is being modeled. Simulations of slowly-sheared crystals using discrete dislocation-dynamics models [162,[194][195][196][197][198][199][200], continuum models [194], phase-field models [201], and phase field crystal models [202] all reveal a broad (power-law) distributions of the serration sizes in the associated stress-strain curves. ...
This paper reviews the recent research and development of high- entropy alloys (HEAs). HEAs are loosely defined as solid solution alloys that contain more than five principal elements in equal or near equal atomic percent (at.%). The concept of high entropy introduces a new path of developing advanced materials with unique properties, which cannot be achieved by the conventional micro-alloying approach based on only one dominant element. Up to date, many HEAs with promising properties have been reported, e.g., high wear-resistant HEAs, Co1.5CrFeNi1.5Ti and Al0.2Co1.5CrFeNi1.5Ti alloys; high-strength body-centered-cubic (BCC) AlCoCrFeNi HEAs at room temperature, and NbMoTaV HEA at elevated temperatures. Furthermore, the general corrosion resis- tance of the Cu0.5NiAlCoCrFeSi HEA is much better than that of the conventional 304-stainless steel. This paper first reviews HEA for- mation in relation to thermodynamics, kinetics, and processing. Physical, magnetic, chemical, and mechanical properties are then discussed. Great details are provided on the plastic deformation, fracture, and magnetization from the perspectives of crackling noise and Barkhausen noise measurements, and the analysis of ser- rations on stress–strain curves at specific strain rates or testing temperatures, as well as the serrations of the magnetization hysteresis loops. The comparison between conventional and high-entropy bulk metallic glasses is analyzed from the viewpoints of eutectic composition, dense atomic packing, and entropy of mixing. Glass forming ability and plastic properties of high- entropy bulk metallic glasses are also discussed. Modeling tech- niques applicable to HEAs are introduced and discussed, such as ab initio molecular dynamics simulations and CALPHAD modeling. Finally, future developments and potential new research directions for HEAs are proposed.
... More recently the crackling noise during plastic deformation is being modeled. Simulations of slowly-sheared crystals using discrete dislocation-dynamics models [162,[194][195][196][197][198][199][200], continuum models [194], phase-field models [201], and phase field crystal models [202] all reveal a broad (power-law) distributions of the serration sizes in the associated stress-strain curves. ...
... More recently the crackling noise during plastic deformation is being modeled. Simulations of slowly-sheared crystals using discrete dislocation-dynamics models [162,[194][195][196][197][198][199][200], continuum models [194], phase-field models [201], and phase field crystal models [202] all reveal a broad (power-law) distributions of the serration sizes in the associated stress-strain curves. ...
This paper reviews the recent research and development of high-entropy alloys (HEAs). HEAs are loosely defined as solid solution alloys that contain more than five principal elements in equal or near equal atomic percent (at.%). The concept of high entropy introduces a new path of developing advanced materials with unique properties, which can’t be achieved by the conventional micro-alloying approach based on only one dominant element. Up to date, many HEAs with promising properties have been reported, e.g., high wear-resistant HEAs, Co1.5CrFeNi1.5Ti and Al0.2Co1.5CrFeNi1.5Ti alloys; high-strength body-centered-cubic (BCC) AlCoCrFeNi HEAs at room temperature, and NbMoTaV HEA at elevated temperatures. Furthermore, the general corrosion resistance of the Cu0.5NiAlCoCrFeSi HEA is much better than that of the conventional 304-stainless steel. This paper first reviews HEA formation in relation to thermodynamics, kinetics, and processing. Physical, magnetic, chemical, and mechanical properties are then discussed. Great details are provided on the plastic deformation, fracture, and magnetization from the perspectives of crackling noise and Barkhausen noise measurements, and the analysis of serrations on stress-strain curves at specific strain rates or testing temperatures, as well as the serrations of the magnetization hysteresis loops. The comparison between conventional and high-entropy bulk metallic glasses is analyzed from the viewpoints of eutectic composition, dense atomic packing, and entropy of mixing. Glass forming ability and plastic properties of high-entropy bulk metallic glasses are also discussed. Modeling techniques applicable to HEAs are introduced and discussed, such as ab initio molecular dynamics simulations and CALPHAD modeling. Finally, future developments and potential new research directions for HEAs are proposed.
This chapter reviews mechanical properties of high-entropy alloys (HEAs) in the fields of hardness, compression, tension, serration behavior, fatigue, and nanoindentation. It shows that the hardness of HEAs varies widely from 140 to 900 HV, highly depending on the alloy systems and related processing methods. The effects of annealing treatment, alloying, and structure on the hardness are discussed. The hardness at high temperatures is also summarized. For compression tests, several parameters of materials, such as Young’s modulus, compressive yield strength, elastic strain, and plastic strain, are determined and discussed. Various loading conditions, such as temperatures, Al contents, strain rates, sample sizes, and aging/annealing effects, are reported to have influence on the microstructural evolution during compression deformation. Microcompression experiments have been performed on HEAs. Even though the study of tensile properties of HEAs is limited to few alloy systems, the effects of structures, grain sizes, alloying elements, and processing parameters on the yielding stress, ductility, and shape of the stress–strain curve, and fracture behavior are discussed. The characteristic elastic behavior is studied by in situ neutron-diffraction techniques during tension. A mean-field theory (MFT) successfully predicts the slip-avalanche and serration statistics observed in recent simulations of plastic deformation of HEAs. Four-point-bending-fatigue tests are conducted on the Al0.5CoCrCuFeNi HEA at various applied loads and reveal that fatigue properties of HEAs could be generally better, compared with conventional alloys and bulk metallic glasses. Nanoindentation studies on the incipient plasticity and creep behavior are discussed. The future work related to mechanical properties of HEAs is suggested at the end.
Plastic deformation is a paradigmatic problem of multiscale materials modelling with relevant processes ranging from the atomistic scale up to macroscopic scales where deformation is treated by continuum mechanics. Recent experiments, investigating deformation fluctuations under conditions where plastic deformation was expected to occur in a smooth and stable manner, demonstrate that deformation is spatially heterogeneous and temporally intermittent, not only on atomic scales, where spatial heterogeneity is expected, but also on mesoscopic scales where plastic fluctuations involve collective events of widely different amplitudes. Evidence for crackling noise in plastic deformation comes from acoustic emission measurements and from deformation of micron-scale samples both in crystalline and amorphous materials. Here we provide a detailed account of our current understanding of crackling noise in crystal and amorphous plasticity stemming from experiments, computational models and scaling theories. We focus our attention on the scaling properties of plastic strain bursts and their interpretation in terms of non-equilibrium critical phenomena.
