A thermally activated dislocation-based constitutive flow model of nanostructured FCC metals involving microstructural evolution

The anisotropic vortex dynamics and phase diagram are determined for a YBa 2 Cu 3 O 7 single crystal with columnar defects oriented at ±7.5° relative to the crystalline c-axis. A second-order splayed-glass to vortex-liquid transition is manifested for magnetic fields nearly parallel to the columns via the critical scaling of vortex AC and DC transport properties. In contrast, for magnetic fields aligned close to the ab-plane, an XY-like vortex-glass transition prevails. For magnetic fields at intermediate angles, there is no evidence of any vortex phase transition, and the vortex dynamics is described in terms of the thermally activated flux flow model.

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Atomistic Simulation of Mobile Defect Clusters in Metals

MRS Proceedings ◽

10.1557/proc-540-649 ◽

1998 ◽

Vol 540 ◽

Cited By ~ 2

Author(s):

Yu.N. Osetsky ◽

D.J. Bacon ◽

A. Serra

Keyword(s):

Stacking Fault ◽

Atomic Scale ◽

Dynamics Simulation ◽

Structure Stability ◽

Dislocation Loops ◽

Fcc Metals ◽

Thermally Activated ◽

Vacancy Loops ◽

Mobile Defect ◽

The Difference

AbstractThe structure, stability and thermally-activated motion of interstitial and vacancy clusters in Fe and Cu have been studied using atomic scale computer simulation. All studied interstitial clusters and perfect interstitial loops (PILs) in Fe are mobile whereas their mobility in Cu can be suppressed at large sizes (bigger than 49–61 self-interstitials depending on the temperature) due to dissociation. A comparative study of relaxed configurations has shown that the structure of small perfect dislocation loops of vacancy and self-interstitial nature is very similar. Molecular dynamics simulation has demonstrated that small perfect vacancy loops (PVLs) in Fe consisting of more than 37 vacancies are stable over a wide temperature range and produce atomic displacements by a thermally-activated movement in the direction of the Burgers vector. The mechanism is qualitatively similar to that of SIA clusters studied earlier. Motion of vacancy loops in Cu does not occur because they transform into sessile configurations similar to stacking fault tetrahedra. These results point to the possibly important contribution of vacancy loop mobility to the difference in radiation damage between bcc and fcc metals, and between fcc metals with different stacking fault energy.

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Flow Stress Modelling and Microstructure Development during Deformation of Metallic Materials

Materials Science Forum ◽

10.4028/www.scientific.net/msf.892.44 ◽

2017 ◽

Vol 892 ◽

pp. 44-49 ◽

Cited By ~ 2

Author(s):

Johannes Kreyca ◽

Ernst Kozeschnik

Keyword(s):

Microstructural Evolution ◽

Elevated Temperatures ◽

Large Strain ◽

Stage Iv ◽

State Parameter ◽

Wire Drawing ◽

Compression Tests ◽

Thermally Activated ◽

Stress Prediction ◽

Subgrain Formation

A constant strain hardening rate is characteristic for large strain deformation at low temperatures and often observed during wire drawing. This stage of deformation, in the following referred to as stage IV, is determined by the microstructural evolution of dislocation cells. At elevated temperatures, rapid stress saturation is typically reached and no stage IV behavior is observed. This behavior is modelled in the present work, following the concept of state-parameter based plasticity, evolving dislocation density and subgrain formation as functions of strain rate, strain and temperature. It is demonstrated that the temperature dependence of state parameters at different deformation stages is closely related. The present model is compared to a series of compression tests carried out on a Gleeble 1500 thermo-mechanical simulator. EBSD micrographs of the same material reveal the microstructural evolution during plastic deformation. It is shown experimentally that the transition from cell forming behavior to subgrain formation correlates well with the disappearance of stage IV and the overall change in the dominant mechanism for overcoming obstacles. In combination with thermally activated yield stress prediction, this model, recently implemented in the software package MatCalc, offers a powerful tool for flow-curve simulation.

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Modeling the Impact of Grain Boundary Properties on Microstructural Evolution

Materials Science Forum ◽

10.4028/www.scientific.net/msf.467-470.707 ◽

2004 ◽

Vol 467-470 ◽

pp. 707-714 ◽

Cited By ~ 2

Author(s):

Anthony D. Rollett

Keyword(s):

Grain Boundary ◽

Grain Growth ◽

Microstructural Evolution ◽

Boundary Energy ◽

Grain Boundary Energy ◽

Fcc Metals ◽

Growth Selection ◽

Component Development ◽

Boundary Properties ◽

The Impact

Much new knowledge has been gained on the properties of grain boundaries that are relevant to processes of microstructural evolution such as grain growth and recrystallization. For mobility, a combination of experiments and numerical simulation has reinforced many of the classical concepts of special crystallographic types with either exceptionally high or exceptionally low mobilities. At another level, the anisotropy of energy of (especially) mobility has long been assumed to play an important role in both grain growth and recrystallization. The process of “micro-growth selection” is assumed to favor, in fcc metals, the development of cube-oriented nuclei in the early stages of recrystallization. We describe simulations in which initial microstructures with varying degrees of verisimilitude to as-deformed microstructures are used, as well as various assumptions about the grain boundary energy and mobility. From these one it is apparent that the anisotropy does indeed effectively promote the cube component development.

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Thermally activated microstructural evolution of sputtered nanostructured Mo–Au

Materialia ◽

10.1016/j.mtla.2018.09.019 ◽

2018 ◽

Vol 4 ◽

pp. 157-165 ◽

Cited By ~ 5

Author(s):

Joel A. Bahena ◽

J. Sebastian Riano ◽

Mohammed R. Chellali ◽

Torben Boll ◽

Andrea M. Hodge

Keyword(s):

Microstructural Evolution ◽

Thermally Activated

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Deformation behavior and strain rate sensitivity of nanostructured materials at moderate temperatures

MRS Proceedings ◽

10.1557/proc-880-bb8.3 ◽

2005 ◽

Vol 880 ◽

Cited By ~ 1

Author(s):

Cécilie Duhamel ◽

Sandrine Guérin ◽

Martin Hÿtch ◽

Yannick Champion

Keyword(s):

Grain Size ◽

Strain Rate ◽

Nanostructured Materials ◽

Strain Rate Sensitivity ◽

Deformation Behavior ◽

Rate Sensitivity ◽

Nanocrystalline Copper ◽

Fcc Metals ◽

Thermally Activated ◽

Increasing Temperature

AbstractStrain-rate jump tests in compression are carried out on nanostructured copper (grain size = 90 nm) at moderate temperatures (353K - 393K). Strain-rate sensitivity m is measured as a function of temperature, T, and strain rate, έ. Increasing temperature or decreasing strain rate induces an increase in the strain-rate sensitivity. For (έ, T) = (1×10-5 s-1, 393K), m is equal to 0.17 which is the highest value reported for nanocrystalline copper. These results of enhanced m are encouraging in terms of gain in ductility. The measurements emphasize the existence of a thermally activated mechanism different from the normal rate-controlling process observed for microcrystalline fcc metals.

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Solvent Induced Morphological Changes to Polycarbonate

MRS Proceedings ◽

10.1557/proc-304-185 ◽

1993 ◽

Vol 304 ◽

Cited By ~ 4

Author(s):

B. J. Briscoe ◽

B. H. Stuart ◽

P. S. Thomas

Keyword(s):

Bisphenol A ◽

Vibrational Spectroscopy ◽

Flow Model ◽

Molecular Level ◽

Morphological Changes ◽

Morphological Properties ◽

Molecular Architecture ◽

Interface Shear ◽

Thermally Activated ◽

Poly Carbonate

AbstractThe interface shear properties of thin bisphenol-A-poly(carbonate) films are measured and interpreted in terms of the effects of the morphology induced by solvent plasticisation. The variations in the interface rheology are discussed in terms of the Eyring stress modified thermally activated flow model. The changes in the molecular architecture, induced by plasticisation, are also examined using vibrational spectroscopy. A correlation is made between the proposed mechanism for microshear and the conveyed morphological properties of the polymer film at the molecular level.

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Stochastic Dislocation Dynamics under Creep Conditions in Metals

MRS Proceedings ◽

10.1557/proc-731-w1.7 ◽

2002 ◽

Vol 731 ◽

Author(s):

Masato Hiratani ◽

Hussein M. Zbib

Keyword(s):

Thermal Fluctuation ◽

Dislocation Motion ◽

Cross Slip ◽

Dislocation Dynamics ◽

Atomistic Simulations ◽

Thermal Processes ◽

New Model ◽

Slip Mechanism ◽

Fcc Metals ◽

Thermally Activated

AbstractA stochastic model is proposed to study dislocation dynamics in metallic single crystals. A Langevin type thermal fluctuation is taken into account for the model to maintain thermal equilibrium. This approach works as Brownian motion of segmental dislocations. Additionally, a new model for implementing the cross slip mechanism in FCC metals is developed based on results obtained by atomistic simulations. This new model is capable of simulating realistic thermal processes such as thermally activated dislocation motion during easy glide or cross slip during cold working of metals.

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Al-TiC Composites Fabricated by a Thermally Activated Reaction Process in an Al Melt Using Al-Ti-C-CuO Powder Mixtures. Part I: Microstructural Evolution and Reaction Mechanism

Metallurgical and Materials Transactions A ◽

10.1007/s11661-014-2476-x ◽

2014 ◽

Vol 45 (12) ◽

pp. 5667-5678 ◽

Cited By ~ 11

Author(s):

Young-Hee Cho ◽

Jung-Moo Lee ◽

Su-Hyeon Kim

Keyword(s):

Reaction Mechanism ◽

Microstructural Evolution ◽

Reaction Process ◽

Powder Mixtures ◽

Thermally Activated

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Atomistic Simulation of Mobile Defect Clusters in Metals

MRS Proceedings ◽

10.1557/proc-538-223 ◽

1998 ◽

Vol 538 ◽

Author(s):

Yu.N. Osetsky ◽

D.J. Bacon ◽

A. Serra

Keyword(s):

Stacking Fault ◽

Atomic Scale ◽

Dynamics Simulation ◽

Structure Stability ◽

Dislocation Loops ◽

Fcc Metals ◽

Thermally Activated ◽

Vacancy Loops ◽

Mobile Defect ◽

The Difference

AbstractThe structure, stability and thermally-activated motion of interstitial and vacancy clusters in Fe and Cu have been studied using atomic scale computer simulation. All studied interstitial clusters and perfect interstitial loops (PILs) in Fe are mobile whereas their mobility in Cu can be suppressed at large sizes (bigger than 49-61 self-interstitials depending on the temperature) due to dissociation. A comparative study of relaxed configurations has shown that the structure of small perfect dislocation loops of vacancy and self-interstitial nature is very similar. Molecular dynamics simulation has demonstrated that small perfect vacancy loops (PVLs) in Fe consisting of more than 37 vacancies are stable over a wide temperature range and produce atomic displacements by a thermally-activated movement in the direction of the Burgers vector. The mechanism is qualitatively similar to that of SIA clusters studied earlier. Motion of vacancy loops in Cu does not occur because they transform into sessile configurations similar to stacking fault tetrahedra. These results point to the possibly important contribution of vacancy loop mobility to the difference in radiation damage between bcc and fcc metals, and between fcc metals with different stacking fault energy.

Download Full-text