On the common topological conditions for shear-coupled twin boundary migration in bcc and hcp metals

Serra, A.; Kvashin, N.; Anento, N.

doi:10.22226/2410-3535-2020-4-537-542

Cited by 8 publications

(10 citation statements)

References 43 publications

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“…More generally, real GBs are rarely symmetric nor flat, nor do they have a pure tilt or pure twist character, and even without preliminary deformation, they contain disconnections of various characters [53]. This defect has been known for decades in phase transformation and twinning [66][67][68][69], but has only recently been considered as the basic brick of shear-coupled GB migration [70][71][72], in metals with bcc and hcp structures too [73,74]. One reason for this late acceptance is that the observation of moving disconnections is complicated experimentally, as in-situ TEM is almost the only way to do it [75] and that many atomistic simulations considered perfect GBs where the disconnection nucleation step overshadows the other mechanisms such as their propagation.…”

Section: Discussionmentioning

confidence: 99%

Shear-coupled migration of grain boundaries: the key missing link in the mechanical behavior of small-grained metals?

Gautier¹,

Rajabzadeh²,

Larranaga³

et al. 2021

Comptes Rendus. Physique

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Section: Discussionmentioning

confidence: 99%

Shear-coupled migration of grain boundaries: the key missing link in the mechanical behavior of small-grained metals?

Gautier¹,

Rajabzadeh²,

Larranaga³

et al. 2021

Comptes Rendus. Physique

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“…Besides the low formation energy of the {112} tilt GB, a relevant feature of this GB for the accommodation of plastic deformation is the existence of highly glissile EDiscs responsible for the shear-coupled GB migration [17,18,24,25]. The critical resolved shear stress of the EDisc is about 20 MPa [54] in Fe.…”

Section: B Elementary Disconnections At the (112) Gbmentioning

confidence: 99%

“…(i) The dislocation at the GB undergoes a variety of feasible processes. The possible reactions of the dislocation present a gradation of complexity, ranging from transmission with a small resistance keeping the same Burgers vector [16] to full absorption by the GB [17,18]. In intermediate situations, the dislocation is partially transmitted, leaving a residual defect at the GB, which is necessary to account for Burgers vector conservation [19].…”

Section: Introductionmentioning

confidence: 99%

“…In partial (total) absorption of the dislocation by the interface, the dislocation is partially (totally) transformed into either GB dislocations (GBDs) at the GB or TB dislocations (TBDs) at the TB. The GBDs and TBDs that step the interface are named disconnections (interfacial line defects with both dislocation and step character [21,22]); among them, we distinguish the gliding elementary disconnections (EDisc) [23], with the Burgers vector parallel to the interface, which are responsible for the shear-coupled boundary migration [17,18,[23][24][25][26][27][28][29] and for the twin growth [30]. The GBDs could favor either the shear-coupled GB migration or the nucleation of other defects such as twins [31][32][33] and dislocations [34]; this behavior occurs in GBs of the most common crystallographic structures in metals, i.e., bcc, fcc, and hcp [23][24][25][26][27][28][29][30][31][32][33][34][35][36][37].…”

Section: Introductionmentioning

confidence: 99%

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Atomic-level study on the interaction of plastic slip with Σ3{112} tilt grain boundary and {112} twins in bcc metals

Kvashin

Anento

Terentyev

et al. 2022

Phys. Rev. Materials

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The 3{112} tilt grain boundary (GB) is found in many grains in bcc polycrystalline metals due to its low energy and high stability. Moreover, it is the coherent boundary of the {112} twin. This paper studies the interaction of a pileup of 1/2 111 dislocations with the {112} GB, extendable to the coherent {112} twin boundary (TB). The results are applied to the interaction of the pileup of dislocations with the {112} twin. The interacting dislocation is transformed into a GB dislocation (or TB dislocation) that acts as a source of disconnections responsible for the shear-coupled GB migration leading to twin growth or shrinkage when the interface is a TB. While a single dislocation cannot be transmitted through the interface, the stress field of the pileup facilitates the transmission if the tensile part of the dislocation core is closer to the interface than the compression part. The {112} twin is found to create barriers to the motion of 1/2 111 crystal dislocations, and the strength of the barrier depends on crystallographic parameters. The results obtained in the slip-TB interaction prove that there is no transmission of dislocations through the twin. Thus, under twinning shear stress, all twins are strong obstacles for the glide of dislocations. Under antitwinnning shear stress, twins with thickness less than a few nanometers (5.6 nm in Fe) are annihilated by the interaction with a pileup of dislocations, contributing to softening, whereas thicker twins block the propagation of dislocations and confine dislocations inside the twin, which contributes to hardening.

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“…Among the variety of disconnections, we define as EDisc the glissile ones that have a Bv parallel to the interfaces [51]. They are responsible for the SCGBM [31,40,49,51,[56][57][58][59]. Thus, the effectiveness of the accommodation of plastic deformation depends on the creation of disconnections, its glissile character and the interaction of these disconnections with other defects located on the GB.…”

Section: Grain Boundaries Under Plastic Deformation Shear-coupled Gb ...mentioning

confidence: 99%

Atomistic study of slip transfer in BCC metals

Kvashin

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(English) The mechanical properties of structural materials, which are naturally polycrystalline, is defined by a number of physical processes that take place at different time and space scales. On several of those processes, bulk dislocations and grain boundaries (GBs) play a relevant role. The plastic deformation in these materials is mainly due to the mobility of dislocations, therefore the interaction of these defects with other pre-existing defects like GBs is a key factor to explain the evolution of the properties over the time. It has been experimentally observed that degradation in the mechanical properties of the steels in service is connected with the formation of slip-bands. Propagation of slip-bands through grain boundaries increases material heterogeneity, leading to premature failure and detrimental loss of ductility. There are many possible types of GBs and the behavior of one specific GB interacting with dislocations cannot be anticipated and consequently must be analyzed individually. Macroscopically, these reactions are classified as absorption, transmission or reflection of dislocations. The relationship of these reactions with the GB structure as well as the external parameters (stress, temperature, etc.) is the objective of this research. The aim of the work is to predict the result of slip bands interaction with GBs based on a multiscale modeling approach. This work presents of a report on the transferability of dislocations through GBs and the role played by the intrinsic defects at GBs. The main goal to achieve is a set of rules to describe the interaction between dislocations and GBs which can be used in larger scale models (OKMC, DD, FEM). The purpose is to improve the description of the microstructure evolution and subsequently, the predicted long-term evolution of the macroscopic properties of the materials of interest, namely ferritic/martensitic steels, which are widely used in nuclear industry for both fusion and fission applications. In order to investigate the mechanisms of the dislocation – GB interaction it is required to access the atomic level, for that reason it has been chosen the Molecular Dynamics modeling technique to carry out this research work. (Español) Las propiedades mecánicas de los materiales estructurales vienen determinadas por una variedad de procesos físicos que tienen lugar a diferentes escalas espaciales y temporales, en los cuales las dislocaciones y las fronteras de grano (FG) juegan un papel relevante. La deformación plástica está directamente relacionada con la movilidad de las dislocaciones, de modo que su interacción con otros defectos preexistentes, como las FG, es un factor clave para explicar la evolución de las propiedades mecánicas con el tiempo. Existe una gran variedad de FG y el comportamiento particular de cada una con las dislocaciones no se puede anticipar y por tanto debe ser analizada individualmente. A nivel microscópico las reacciones posibles son absorción, transmisión o reflexión de las dislocaciones. Establecer la conexión entre dichas reacciones y la estructura de las FG, así como con parámetros externos (esfuerzo, temperatura, etc.) es el propósito de este estudio. La finalidad es predecir el resultado de la interacción de las bandas de deformación con las FG basándonos en la aproximación de la modelización mulfiescala. Se presenta un informe sobre la transferibilidad de las dislocaciones a través de las FG y el papel jugado por los defectos intrínsecos de la interface. El objetivo principal es investigar el papel que tiene la estructura atómica de las FG en la interacción con dislocaciones a fin de obtener un conjunto de reglas que puedan ser fácilmente transferibles a otros modelos que trabajen a unas escalas espaciales y temporales superiores, por ejemplo, la Dinámica de Dislocaciones. A fin de estudiar los mecanismos de interacción entre la dislocación y la FG se requiere usar una aproximación a nivel atómico, por esta razón el método de modelización escogido ha sido la Dinámica Molecular (DM). Este trabajo presenta los resultados de modelización por DM realizada para estudiar los mecanismos de interacción entre dislocaciones y FG de inclinación simétrica, ya que estas representan a un número significativo de interfaces presentes en materiales reales. Para cada FG considerada se ha realizado un análisis de los resultados que nos ha permitido obtener una descripción de la dependencia del tipo de reacción con la temperatura y el esfuerzo aplicado. Los resultados obtenidos se usan como datos de entrada para la segunda etapa del trabajo, que incluye la ovansión de la caja de simulación para la modelización 3-D, con el fin de estudiar la interacción entre dislocaciones de frontera y defectos de irradiación situados en la interface. Se han obtenido nuevos datos de gran valor que dan una nueva perspectiva respecto de los procesos a nivel atómico asociados a la interacción FG-dislocaciones en acero. Por ejemplo, se ha descubierto el papel clave de las desconexiones elementales en dichas interacciones. Debido a que el esfuerzo crítico necesario para activar su movimiento en la FG {1 12} es muy bajo, el mecanismo de migración de la FG acoplada a la deformación es muy eficiente. Esta FG es la única en la que se ha observado transmisión de la pila de dislocaciones, ya que basta con una sola desconexión para transformar el vector de Burgers de la dislocación absorbida, haciendo que sea capaz de desplazarse hacia el grano adyacente. Para el resto de FG estudiadas no observado transmisión v La-FG {332} es capaz de y absorber varias dislocaciones formando unas interficies asimétricas en la zona de interacción. Respecto a la FG {1 16} es capaz de acomodar la deformación por medio de reacciones con más de un tipo de desconexión elemental. Por el contrario, la ausencia de desconexiones en la FG {1 1 1} impide su migración, no así su transformación en nuevas interficies. La adecuada elección de FG nos ha permitido extraer conclusiones suficientemente generales para ser usadas en el desarrollo de modelos a mayor escala, que son las herramientas indispensables para investigar la evolución a largo plazo ...

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On the common topological conditions for shear-coupled twin boundary migration in bcc and hcp metals

Cited by 8 publications

References 43 publications

Shear-coupled migration of grain boundaries: the key missing link in the mechanical behavior of small-grained metals?

Shear-coupled migration of grain boundaries: the key missing link in the mechanical behavior of small-grained metals?

Atomic-level study on the interaction of plastic slip with Σ3{112} tilt grain boundary and {112} twins in bcc metals

Atomistic study of slip transfer in BCC metals

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