Materials Theory最新文献_第5页

Slip-free multiplication and complexity of dislocation networks in FCC metals FCC金属中位错网络的无滑移倍增和复杂性

Materials Theory Pub Date : 2021-03-29 DOI: 10.1186/s41313-020-00024-y

Sh. Akhondzadeh, Nicolas Bertin, Ryan B. Sills, Wei Cai

{"title":"Slip-free multiplication and complexity of dislocation networks in FCC metals","authors":"Sh. Akhondzadeh, Nicolas Bertin, Ryan B. Sills, Wei Cai","doi":"10.1186/s41313-020-00024-y","DOIUrl":"https://doi.org/10.1186/s41313-020-00024-y","url":null,"abstract":"During plastic deformation of crystalline solids, intricate networks of dislocation lines form and evolve. To capture dislocation density evolution, prominent theories of crystal plasticity assume that 1) multiplication is driven by slip in active slip systems and 2) pair-wise slip system interactions dominate network evolution. In this work, we analyze a massive database of over 100 discrete dislocation dynamics simulations (with cross-slip suppressed), and our findings bring both of these assumptions into question. We demonstrate that dislocation multiplication is commonly observed on slip systems with no applied stress and no plastic strain rate, a phenomenon we refer to as slip-free multiplication. We show that while the formation of glissile junctions provides one mechanism for slip-free multiplication, additional mechanisms which account for the influence of coplanar interactions are needed to fully explain the observations. Unlike glissile junction formation which results from a binary reaction between a pair of slip systems, these new multiplication mechanisms require higher order reactions that lead to complex network configurations. While these complex configurations have not been given much attention previously, they account for about 50% of the line intersections in our database.","PeriodicalId":693,"journal":{"name":"Materials Theory","volume":"5 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-03-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1186/s41313-020-00024-y","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"5124764","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 8

On the three-dimensional spatial correlations of curved dislocation systems 论弯曲位错体系的三维空间相关性

Materials Theory Pub Date : 2021-03-10 DOI: 10.1186/s41313-020-00026-w

Joseph Pierre Anderson, Anter El-Azab

{"title":"On the three-dimensional spatial correlations of curved dislocation systems","authors":"Joseph Pierre Anderson, Anter El-Azab","doi":"10.1186/s41313-020-00026-w","DOIUrl":"https://doi.org/10.1186/s41313-020-00026-w","url":null,"abstract":"Coarse-grained descriptions of dislocation motion in crystalline metals inherently represent a loss of information regarding dislocation-dislocation interactions. In the present work, we consider a coarse-graining framework capable of re-capturing these interactions by means of the dislocation-dislocation correlation functions. The framework depends on a convolution length to define slip-system-specific dislocation densities. Following a statistical definition of this coarse-graining process, we define a spatial correlation function which will allow the arrangement of the discrete line system at two points—and thus the strength of their interactions at short range—to be recaptured into a mean field description of dislocation dynamics. Through a statistical homogeneity argument, we present a method of evaluating this correlation function from discrete dislocation dynamics simulations. Finally, results of this evaluation are shown in the form of the correlation of dislocation densities on the same slip-system. These correlation functions are seen to depend weakly on plastic strain, and in turn, the dislocation density, but are seen to depend strongly on the convolution length. Implications of these correlation functions in regard to continuum dislocation dynamics as well as future directions of investigation are also discussed.","PeriodicalId":693,"journal":{"name":"Materials Theory","volume":"5 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-03-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1186/s41313-020-00026-w","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4429324","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 8

Length scales and scale-free dynamics of dislocations in dense solid solutions 密集固溶体中位错的长度尺度和无标度动力学

Materials Theory Pub Date : 2020-11-04 DOI: 10.1186/s41313-020-00023-z

Gábor Péterffy, Péter D. Ispánovity, Michael E. Foster, Xiaowang Zhou, Ryan B. Sills

{"title":"Length scales and scale-free dynamics of dislocations in dense solid solutions","authors":"Gábor Péterffy, Péter D. Ispánovity, Michael E. Foster, Xiaowang Zhou, Ryan B. Sills","doi":"10.1186/s41313-020-00023-z","DOIUrl":"https://doi.org/10.1186/s41313-020-00023-z","url":null,"abstract":"The fundamental interactions between an edge dislocation and a random solid solution are studied by analyzing dislocation line roughness profiles obtained from molecular dynamics simulations of Fe0.70Ni0.11Cr0.19 over a range of stresses and temperatures. These roughness profiles reveal the hallmark features of a depinning transition. Namely, below a temperature-dependent critical stress, the dislocation line exhibits roughness in two different length scale regimes which are divided by a so-called correlation length. This correlation length increases with applied stress and at the critical stress (depinning transition or yield stress) formally goes to infinity. Above the critical stress, the line roughness profile converges to that of a random noise field. Motivated by these results, a physical model is developed based on the notion of coherent line bowing over all length scales below the correlation length. Above the correlation length, the solute field prohibits such coherent line bow outs. Using this model, we identify potential gaps in existing theories of solid solution strengthening and show that recent observations of length-dependent dislocation mobilities can be rationalized.","PeriodicalId":693,"journal":{"name":"Materials Theory","volume":"4 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1186/s41313-020-00023-z","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4181248","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 12

Probing the transition from dislocation jamming to pinning by machine learning 用机器学习方法探讨位错干扰到钉住的转变

Materials Theory Pub Date : 2020-10-09 DOI: 10.1186/s41313-020-00022-0

Henri Salmenjoki, Lasse Laurson, Mikko J. Alava

{"title":"Probing the transition from dislocation jamming to pinning by machine learning","authors":"Henri Salmenjoki, Lasse Laurson, Mikko J. Alava","doi":"10.1186/s41313-020-00022-0","DOIUrl":"https://doi.org/10.1186/s41313-020-00022-0","url":null,"abstract":"Collective motion of dislocations is governed by the obstacles they encounter. In pure crystals, dislocations form complex structures as they become jammed by their anisotropic shear stress fields. On the other hand, introducing disorder to the crystal causes dislocations to pin to these impeding elements and, thus, leads to a competition between dislocation-dislocation and dislocation-disorder interactions. Previous studies have shown that, depending on the dominating interaction, the mechanical response and the way the crystal yields change.Here we employ three-dimensional discrete dislocation dynamics simulations with varying density of fully coherent precipitates to study this phase transition ? from jamming to pinning ? using unsupervised machine learning. By constructing descriptors characterizing the evolving dislocation configurations during constant loading, a confusion algorithm is shown to be able to distinguish the systems into two separate phases. These phases agree well with the observed changes in the relaxation rate during the loading. Our results also give insights on the structure of the dislocation networks in the two phases.","PeriodicalId":693,"journal":{"name":"Materials Theory","volume":"4 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1186/s41313-020-00022-0","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4402765","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 6

Symmetry breaking during defect self-organization under irradiation 辐照下缺陷自组织的对称性破缺

Materials Theory Pub Date : 2020-05-24 DOI: 10.1186/s41313-020-00021-1

Yongfeng Zhang, Yipeng Gao, Cheng Sun, Daniel Schwen, Chao Jiang, Jian Gan

{"title":"Symmetry breaking during defect self-organization under irradiation","authors":"Yongfeng Zhang, Yipeng Gao, Cheng Sun, Daniel Schwen, Chao Jiang, Jian Gan","doi":"10.1186/s41313-020-00021-1","DOIUrl":"https://doi.org/10.1186/s41313-020-00021-1","url":null,"abstract":"One of the most intriguing phenomena under radiation is the self-organization of defects, such as the void superlattices, which have been observed in a list of bcc and fcc metals and alloys when the irradiation conditions fall into certain windows defined by temperature and dose rate. A superlattice features a lattice parameter and a crystal structure. Previously, it has been shown that the superlattice parameter is given by the wavelength of vacancy concentration waves that develop when the uniform concentration field becomes unstable. This instability is driven thermodynamically by vacancy concentration supersaturation and affected by the irradiation condition. However, a theory that predicts the superlattice symmetry, i.e., the selection of superlattice structure, has remained missing decades after the first report of superlattices. By analyzing the nonlinear recombination between vacancies and self-interstitial-atoms (SIAs) in the discrete lattice space, this work establishes the physical connection between symmetry breaking and anisotropic SIA diffusion, allowing for predictions of void ordering during defect self-organization. The results suggest that while the instability is driven thermodynamically by vacancy supersaturation, the symmetry development is kinetically rather than thermodynamically driven. The significance of SIA diffusion anisotropy in affecting superlattice formation under irradiation is also indicated. Various superlattice structures can be predicted based on different SIA diffusion modes, and the predictions are in good agreement with atomistic simulations and previous experimental observations.","PeriodicalId":693,"journal":{"name":"Materials Theory","volume":"4 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-05-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1186/s41313-020-00021-1","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"5295914","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 7

A Filon-like integration strategy for calculating exact exchange in periodic boundary conditions: a plane-wave DFT implementation 计算周期边界条件下精确交换的类filon积分策略:平面波DFT实现

Materials Theory Pub Date : 2020-04-17 DOI: 10.1186/s41313-020-00019-9

Eric J Bylaska, Kevin Waters, Eric D Hermes, Judit Zádor, Kevin M Rosso

{"title":"A Filon-like integration strategy for calculating exact exchange in periodic boundary conditions: a plane-wave DFT implementation","authors":"Eric J Bylaska, Kevin Waters, Eric D Hermes, Judit Zádor, Kevin M Rosso","doi":"10.1186/s41313-020-00019-9","DOIUrl":"https://doi.org/10.1186/s41313-020-00019-9","url":null,"abstract":"An efficient and accurate approach for calculating exact exchange and other two-electron integrals has been developed for periodic electronic structure methods. Traditional approaches used for integrating over the Brillouin zone in band structure calculations, e.g. trapezoidal or Monkhorst-Pack, are not accurate enough for two-electron integrals. This is because their integrands contain multiple singularities over the double integration of the Brillouin zone, which with simple integration methods lead to very inaccurate results. A common approach to this problem has been to replace the Coulomb interaction with a screened Coulomb interaction that removes singularities from the integrands in the two-electron integrals, albeit at the inelegance of having to introduce a screening factor which must precomputed or guessed. Instead of introducing screened Coulomb interactions in an ad hoc way, the method developed in this work derives an effective screened potential using a Filon-like integration approach that is based only on the lattice parameters. This approach overcomes the limitations of traditionally defined screened Coulomb interactions for calculating two-electron integrals, and makes chemistry many-body calculations tractable in periodic boundary conditions. This method has been applied to several systems for which conventional DFT methods do not work well, including the reaction pathways for the addition of H2 to phenol and Au(_{20}^{-}) nanoparticle, and the electron transfer of a charge trapped state in the Fe(II) containing mica, annite.","PeriodicalId":693,"journal":{"name":"Materials Theory","volume":"4 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-04-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1186/s41313-020-00019-9","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4669080","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 4

Mechanics of moving defects in growing sheets: 3-d, small deformation theory 生长片中运动缺陷的力学:三维小变形理论

Materials Theory Pub Date : 2020-04-16 DOI: 10.1186/s41313-020-00018-w

Amit Acharya, Shankar C. Venkataramani

引用次数: 6

Theoretical framework for predicting solute concentrations and solute-induced stresses in finite volumes with arbitrary elastic fields 预测具有任意弹性场的有限体积中溶质浓度和溶质诱发应力的理论框架

Materials Theory Pub Date : 2020-04-07 DOI: 10.1186/s41313-020-00020-2

Yejun Gu, Jaafar A. El-Awady

{"title":"Theoretical framework for predicting solute concentrations and solute-induced stresses in finite volumes with arbitrary elastic fields","authors":"Yejun Gu, Jaafar A. El-Awady","doi":"10.1186/s41313-020-00020-2","DOIUrl":"https://doi.org/10.1186/s41313-020-00020-2","url":null,"abstract":"A theoretical model for computing the interstitial solute concentration and the interstitial solute-induced stress field in a three-dimensional finite medium with any arbitrary elastic fields was developed. This model can be directly incorporated into two-dimensional or three-dimensional discrete dislocation dynamics simulations, continuum dislocation dynamics simulations, or crystal plasticity simulations. Using this model, it is shown that a nano-hydride can form in the tensile region below a dissociated edge dislocation at hydrogen concentration as low as χ0=5×10?5, and its formation induces a localized hydrogen elastic shielding effect that leads to a lower stacking fault width for the edge dislocation. Additionally, the model also predicts the segregation of hydrogen at Σ109(13 7 0)/33.4° symmetric tilt grain boundary dislocations. This segregation strongly alters the magnitude of the shear stresses at the grain boundary, which can subsequently alter dislocation-grain boundary interactions and dislocation slip transmissions across the grain boundary. Moreover, the model also predicts that the hydrogen concentration at a mode-I central crack tip increases with increasing external loading, higher intrinsic hydrogen concentration, and/or larger crack lengths. Finally, linearized approximate closed-form solutions for the solute concentration and the interstitial solute-induced stress field were also developed. These approximate solutions can effectively reduce the computation cost to assess the concentration and stress field in the presence of solutes. These approximate solutions are also shown to be a good approximation when the positions of interest are several nanometers away (i.e. long-ranged elastic interactions) from stress singularities (e.g. dislocation core and crack tip), for low solute concentrations, and/or at high temperatures.","PeriodicalId":693,"journal":{"name":"Materials Theory","volume":"4 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-04-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1186/s41313-020-00020-2","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4280046","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 6

Brittle to quasi-brittle transition and crack initiation precursors in crystals with structural Inhomogeneities 结构不均匀晶体的脆性到准脆性转变和裂纹萌生前体

Materials Theory Pub Date : 2019-11-01 DOI: 10.1186/s41313-019-0017-0

S. Papanikolaou, P. Shanthraj, J. Thibault, C. Woodward, F. Roters

{"title":"Brittle to quasi-brittle transition and crack initiation precursors in crystals with structural Inhomogeneities","authors":"S. Papanikolaou, P. Shanthraj, J. Thibault, C. Woodward, F. Roters","doi":"10.1186/s41313-019-0017-0","DOIUrl":"https://doi.org/10.1186/s41313-019-0017-0","url":null,"abstract":"Crack initiation emerges due to a combination of elasticity, plasticity, and disorder, and it displays strong dependence on the material’s microstructural details. The characterization of the structural uncertainty in the original microstructure is typically empirical and systematic characterization protocols are lacking. In this paper, we propose an investigational tool in the form of the curvature of an ellipsoidal notch: As the radius of curvature at the notch increases, there is a dynamic phase transition from notch-induced crack initiation to disorder-induced crack nucleation. We argue that the this transition may unveil the characteristic length scale of structural disorder in the material. We investigate brittle but elastoplastic metals with continuum, microstructural disorder that could originate in a manufacturing process, such as alloying. We perform extensive and realistic simulations, using a phase-field approach coupled to crystal plasticity, where microstructural disorder and notch width are systematically varied. We identify the brittle-to-quasi-brittle transition for various disorder strengths in terms of the damage and stress evolution. Moreover, we investigate precursors to crack initiation that we quantify in terms of the expected stress drops during displacement control loading.","PeriodicalId":693,"journal":{"name":"Materials Theory","volume":"3 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1186/s41313-019-0017-0","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4051796","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 12

Overdamped langevin dynamics simulations of grain boundary motion 晶界运动的过阻尼朗格万动力学模拟

Materials Theory Pub Date : 2019-05-27 DOI: 10.1186/s41313-019-0016-1

Carolina Baruffi, Alphonse Finel, Yann Le Bouar, Brigitte Bacroix, Oguz Umut Salman

引用次数: 12