The work-hardening of copper-silica

Brown, L. M.; Stobbs, W. M.

doi:10.1080/14786437108217406

Cited by 320 publications

(73 citation statements)

References 14 publications

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“…This confirms that the strength of nickel alloys is mainly controlled by the dislocation-precipitates interaction, especially the accumulation of dislocation loops at the matrix-precipitate interfaces. These accumulated dislocation loops form a strong network and make the mobile dislocations more difficult to bow-out between the precipitates, leading to significant strain-hardening effect [37,38]. As also demonstrated in Huang et al.…”

Section: Dislocation-precipitate Interactionmentioning

confidence: 61%

3D DDD modelling of dislocation–precipitate interaction in a nickel-based single crystal superalloy under cyclic deformation

Lin

Huang

Zhao

et al. 2018

Philosophical Magazine

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Section: Dislocation-precipitate Interactionmentioning

confidence: 61%

3D DDD modelling of dislocation–precipitate interaction in a nickel-based single crystal superalloy under cyclic deformation

Lin

Huang

Zhao

et al. 2018

Philosophical Magazine

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“…We stress that this is the first case where the Hirsch mechanism is dynamically observed, while TEM observations have detected only the resultant structures. Note that the mechanism of Brown and Stobbs [12] has not been observed in the conditions investigated here. More importantly, it is found that the Hirsch mechanism always occurs for the condition I, while the Orowan mechanism is realized for the condition II.…”

mentioning

confidence: 85%

“…This mechanism is named after Hirsch and referred to as the Hirsch mechanism. On the other hand, Brown and Stobbs presented another mechanism where a dislocation loop of a secondary Burgers vector nucleates on the precipitate surface [12]. In both cases, the resultant structure is a row of prismatic loops which was experimentally observed by transmission electron microscopy (TEM) [11,12,13].…”

mentioning

confidence: 99%

Dynamics of a dislocation bypassing an impenetrable precipitate: The Hirsch mechanism revisited

Hatano

2006

Phys. Rev. B

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Dynamical process where an edge dislocation in fcc copper bypasses an impenetrable precipitate is investigated by means of molecular dynamics simulation. A mechanism which is quite different from the Orowan mechanism is observed, where a dislocation leaves two prismatic loops near a precipitate: i.e. the Hirsch mechanism. It is found that the critical stress for the Hirsch mechanism is almost the same as the Orowan stress, while the spatial inhomogeneity of the shear stress is essential to the Hirsch mechanism. We also find that the repetition of the Hirsch mechanism does not increase the critical stress.PACS numbers: 81.40. Cd, 61.72.Bb, 62.20.Fe Plastic flow in crystalline materials is mainly dominated by the movement of dislocations. They are curvilinear defects which can move at much lower stress levels than the theoretical strength of a perfect crystal [1]. A dislocation interacts with other lattice defects such as voids or precipitates, which obstruct the dislocation motion to result in hardening. Such dislocation-obstacle interactions dominate plasticity of crystalline materials, and hence they are one of the major concerns in materials science. Until very recently, they were considered exclusively by plausible continuum models [2,3], which deal with a single glide plane and neglect atomistic discreteness. The recent computer development enables direct molecular dynamics (MD) simulation on dislocation systems, which consist of multi-million atoms. MD simulations have revealed dynamical properties and atomistic details of dislocations. For example, edge dislocations absorb vacancies when they interact with voids [4] or stacking fault tetrahedra [5]. They are good illustrations of the usefulness of MD simulation in the field of dislocation physics. Along the line of these studies, the interaction with an impenetrable precipitate, which has not been investigated by MD simulation, is explored in this Letter.An interaction between a dislocation and a precipitate is characterized by their shear moduli. When the shear modulus of a precipitate is larger than the bulk's, the interaction is repulsive so that the precipitate can be impenetrable [6]. In this case, the extent of hardening becomes significant. This is the principle of so-called "particle strengthening", which is widely utilized in processing stronger materials [7]. There is a mechanism by which a dislocation bypasses impenetrable obstacles, where a dislocation largely bows out to leave a dislocation loop around the obstacle [1]. Note that the loop is on the original glide plane. This process and the resultant dislocation loop are referred to as the Orowan mechanism and an Orowan loop, respectively. However, because the interaction between an Orowan loop and a dislocation is strongly repulsive, theoretical calculations in which Orowan loops are assumed to be persistent predict unreasonably strong work-hardening [8,9]. To avoid this contradiction, some alternative bypass mechanisms have been presented. Hirsch [10,11] had pointed out the possibility of...

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“…We assume for the case of interest here---namely the formation of a cylindrical or spherical plastic zone of tangled dislocations surrounding the inclusion--that the impeding effect of one dislocation upon motion of another can be represented by equation (7). The same relationship was used by Brown and Stobbs [45] to model strainhardening in the plastic zone around submicroscopic particles in a deformed copper-silica system. We make the added assumptions that flow stress and dislocation density are uniform within the plastic zone and that the plastic zone size always increases with increasing AT.…”

Section: L(i-v) Cry)mentioning

confidence: 97%

On plastic relaxation of thermal stresses in reinforced metals

Dunand

Mortensen

1991

Acta Metallurgica et Materialia

163

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Abstract--Silver chloride containing alumina fibers or glass microspheres is used as a model material to study matrix plasticity induced by thermal mismatch in metal matrix composites. Resulting matrix dislocations are decorated at room temperature in the bulk material and observed by optical microscopy. Plastic deformation of the matrix around the inclusions is found to take the form of (i) rows of prismatic dislocation loops punched into the matrix and/or (ii) a plastic zone containing tangled dislocations surrounding the inclusions. From the number of loops punched by spheres, the temperature interval over which slip of prismatic loops is operative is calculated to be 100 + 30 K wide. The stress in the plastic zone around fibers is determined from the radius of curvature of pinned dislocations, leading to the conclusion that the matrix is locally strain-hardened. A simple model taking this fact into account is proposed to predict the radius of the plastic zone around embedded cylinders and spheres and is compared to the experimental data.Rrsum~-Le chlorure d'argent contenant des fibres d'alumine ou des microsphrres de verre est utilis6 pour 6tudier la plasticit6 induite par incompatibilit6 thermique darts la matrice de matrriaux composites matrice m&allique. Les dislocations qui en rrsultent sont drcorres dans la matrice ~i temprrature ambiante et observres par microscopie optique. La drformation plastique de la matrice autour de ces inclusions se manifeste par (i) des rangres de boucles de dislocations prismatiques et/ou (ii) une zone plastique contenant des dislocations emmrlres autour des inclusions. A partir du nombre de boucles engendrres par les sphrres, une valeur de I00 _.+ 30 K est calculre pour l'intervale de temprrature pendant lequel le glissement de boucles prismatiques est oprrationel. La tension dans la zone plastique autour de la fibre est ddterminre ~. partir du rayon de courbure de dislocations bloqures, ce qui conduit ~ la conclusion que la matrice est localement 6crouie. Un modrle simple tenant compte de ce fait est propos6 pour prrdire le rayon de la zone platique autour de cylindres ou de sphdres et compar6 aux donnres exprrimentales.Zusammenfassung--Silberchlorid mit Aluminiumoxid Fasern oder Glassmikrokugeln wird als Modellmaterial beniitzt, um die thermisch induzierte Matrixplastizit/it in Verbundwerkstoffen mit metallischer Matrix zu studieren. Resultierende Matrixversetzungen werden bei Raumtemperatur im Materialinnern dekoriert und durch optische Mikroskopie beobachtet. Plastische Verformung der Matrix um die Einschlfisse wird in Form von (i) Reihen yon in die Matrix ausgestossenen prismatischen Versetzungsringen und/oder (ii) einer plastischen Zone, die Versetzunganh/iufungen um den Einschluss enth/ilt, beobachtet. Aus der Zahl der von den Kugeln ausgestossenen Ringen wird das Temperaturinterval, w/ihrend dessen Gleitung prismatischer Ringe wirksam ist, als 100 + 30 K ausgerechnet. Die Spannung in der plastischen Zone um die Fasern wird aus dem Kriimmungsradius blockierter Versetz...

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The work-hardening of copper-silica

Cited by 320 publications

References 14 publications

3D DDD modelling of dislocation–precipitate interaction in a nickel-based single crystal superalloy under cyclic deformation

3D DDD modelling of dislocation–precipitate interaction in a nickel-based single crystal superalloy under cyclic deformation

Dynamics of a dislocation bypassing an impenetrable precipitate: The Hirsch mechanism revisited

On plastic relaxation of thermal stresses in reinforced metals

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