Latent hardening in copper and aluminium single crystals

Franciosi, P.; Berveiller, M.; Zaoui, A.

doi:10.1016/0001-6160(80)90162-5

Cited by 474 publications

(209 citation statements)

References 17 publications

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“…This hypothesis is supported by both experimental evidence [19,22,26,27] and MD simulation results [28][29][30]. First, experimental studies on the latent hardening of Al and Cu revealed that L-C locks are most effective in producing hardening among all dislocation barriers formed by dislocation intersections [18,25,26]. This observation is believed to be typical of fcc metals with medium-to-high stacking fault energies.…”

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confidence: 65%

Strong Strain Hardening in Nanocrystalline Nickel

et al. 2009

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Low strain hardening has hitherto been considered an intrinsic behavior for most nanocrystalline (NC) metals, due to their perceived inability to accumulate dislocations. In this Letter, we show strong strain hardening in NC nickel with a grain size of $20 nm under large plastic strains. Contrary to common belief, we have observed significant dislocation accumulation in the grain interior. This is enabled primarily by Lomer-Cottrell locks, which pin the lock-forming dislocations and obstruct dislocation motion. These observations may help with developing strong and ductile NC metals and alloys.

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confidence: 65%

Strong Strain Hardening in Nanocrystalline Nickel

et al. 2009

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“…Our solution includes the case in which the density of point obstacles is a function of time. Following Franciosi and co-workers (Franciosi et al 1980, Franciosi and Zaoui 1982, Franciosi 1983, 1985ab, 1988, the strength of the short-range obstacles introduced by forest dislocations is taken to be a function of the mode of interaction, e.g. of whether the intersecting dislocations react to form junctions.…”

Section: Introductionmentioning

confidence: 99%

Computational modelling of single crystals

Cuitiño

Ortiz

1993

Modelling Simul. Mater. Sci. Eng.

349

224

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Abstract. The physical basis of computationally uactable models of crystalline plasticity iS reviewed. A statistical mechanical model of dislocation motion throu@ forest dislocations is formulated. Following Franciosi and co-workers, the strength of lhe ShoR-range oblacles introduced by the forest dislocations is allowed to depend on the mode of interaction. The kinetic equations governing dislocation motion are solved in closed form for monotonic loading. with Vansienft in the densiry of fomt dislocations accounled for. This solution, coupled wilh svilable equations of evolution for the dislocation densities, provides a complete descripticn of the hardening of crystals under monotonic loading. Detailed comparisons with experiment demonstrate the predictive capabilities of the theory. An adaptive finite element formulation for the analysis of ductile single crystals is also developed. Calculations of the near-tip fields in CU single crys& illustrate the versatility of the m e t h o d .

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“…Though we have made a systematic study of a number of dislocation junctions found in fcc materials, we concentrate here only on the case of the Lomer-Cottrell junction. Our reason for limiting the discussion is the presumed importance of the Lomer-Cottrell junction in governing the hardening of fcc materials as deduced from experimental analyses [2].Our ambition in the pages that follow is to examine the atomic-level structure of the Lomer-Cottrell junction both in the absence and presence of an externally applied stress. The response of a junction to an applied stress is of prime importance since, in macroscopic descriptions of hardening [7], obstacles to dislocation motion such as junctions are represented by parameters derived from the stress needed to force the dislocations across the obstacles of interest.…”

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confidence: 99%

Structure and Strength of Dislocation Junctions: An Atomic Level Analysis

1999

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The quasicontinuum method is used to simulate three-dimensional Lomer-Cottrell junctions both in the absence and in the presence of an applied stress. The simulations show that this type of junction is destroyed by an unzipping mechanism in which the dislocations that form the junction are gradually pulled apart along the junction segment. The calculated critical stress needed for breaking the junction is comparable to that predicted by line tension models. The simulations also demonstrate a strong influence of the initial dislocation line directions on the breaking mechanism, an effect that is neglected in the macroscopic treatment of the hardening effect of junctions.The mechanical properties of a wide range of materials can be traced in part to the motion and interaction of dislocations. Dislocation junctions serve as one class of obstacles to dislocation motion. From the standpoint of work hardening, junctions have been implicated as a primary contributor to the observed increase in the flow stress with increasing dislocation density [1]. They are one example of "dislocation chemistry" in which dislocations can join and dissociate to form new segments. Such reactions involve both atomic and elastic effects since in the core regions there are substantial atomic rearrangements, while at larger distances the dislocations still interact elastically.Until now, the vast majority of information concerning dislocation junctions has been obtained either from macroscopic hardening experiments [2] or models deriving from elasticity theory [3,4]. On the other hand, evidence has been mounting for decades that in certain circumstances dislocation core effects play a critical role in determining the actual behavior of materials [5], and recent calculations have shown that atomic level insights can be gained with respect to junctions as well [6]. The calculations undertaken here attempt to account for both the long range elastic interactions and the detailed atomic level geometries that give junctions their overall behavior. Though we have made a systematic study of a number of dislocation junctions found in fcc materials, we concentrate here only on the case of the Lomer-Cottrell junction. Our reason for limiting the discussion is the presumed importance of the Lomer-Cottrell junction in governing the hardening of fcc materials as deduced from experimental analyses [2].Our ambition in the pages that follow is to examine the atomic-level structure of the Lomer-Cottrell junction both in the absence and presence of an externally applied stress. The response of a junction to an applied stress is of prime importance since, in macroscopic descriptions of hardening [7], obstacles to dislocation motion such as junctions are represented by parameters derived from the stress needed to force the dislocations across the obstacles of interest.Although such an investigation demands an atomic level calculation, it is also evident that three-dimensional calculations of this sort require an enormous computational investment. As an alternat...

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Latent hardening in copper and aluminium single crystals

Cited by 474 publications

References 17 publications

Strong Strain Hardening in Nanocrystalline Nickel

Strong Strain Hardening in Nanocrystalline Nickel

Computational modelling of single crystals

Structure and Strength of Dislocation Junctions: An Atomic Level Analysis

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