HREM imaging of single unit cell carbide precipitates in Pt-C alloys

Dilute Pt-C alloys are prototypical for studying oversize carbide phase precipitation from interstitial solid solution. Earlier studies showed the essential function of quenched-in vacancies in the precipitation process. Vacancies play a dual, volume accommodation and structural, role in the transformation by modifying both the habit plane spacing and stacking sequence. It was also shown how the precipitation sequence in interstitial Pt-C alloys is analogous to that in substitutional Al-Cu alloys. Initially a “GP zone” consisting of a monolayer plate of carbon atoms and vacancies forms. Atomic resolution images of the socalled a precipitates have confirmed their structure. During subsequent coarsening of the precipitates, α’ platelets form. Schematic diagrams illustrating the α and α’ structures in <100> projection are given in Fig. 1. The single-layer a structure, or GP zone is identical to a ﹛100﹜ stacking fault stabilized by an intercalation of carbon. The two-layer α’ structure is the first true precipitate phase and has a crystal structure anti-isomorphous with calcium fluoride.

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Competing nucleation of single- and double-layer Guinier–Preston zones in Al–Cu alloys

Scientific Reports ◽

10.1038/s41598-021-83920-8 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Hiroshi Miyoshi ◽

Hajime Kimizuka ◽

Akio Ishii ◽

Shigenobu Ogata

Keyword(s):

Double Layer ◽

Formation Enthalpy ◽

Single Layer ◽

Nucleation Theory ◽

Classical Nucleation Theory ◽

Critical Conditions ◽

Precipitation Process ◽

Cu Alloys ◽

Engineering Alloys ◽

Underlying Mechanisms

AbstractSolid-state precipitation is a key heat-treatment strategy for strengthening engineering alloys. Therefore, predicting the precipitation process of localized solute-rich clusters, such as Guinier–Preston (GP) zones, is necessary. We quantitatively evaluated the critical nucleus size and nucleation barrier of GP zones in Al–Cu alloys, illustrating the precipitation preferences of single-layer (GP1) and double-layer (GP2) GP zones. Based on classical nucleation theory using an effective multi-body potential for dilute Al–Cu systems, our model predicted GP1 and GP2 precipitation sequences at various temperatures and Cu concentrations in a manner consistent with experimental observations. The crossover between formation enthalpy curves of GP1 and GP2 with increasing cluster size determines the critical conditions under which GP2 zones can nucleate without prior formation of GP1 zones. This relationship reflects competing interactions within and between clusters. The results illustrate the underlying mechanisms of competing nucleation between zones, and provide guidance for tailoring aging conditions to achieve desired mechanical properties for specific applications.

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The Natural Aging Effect on the Activation Energy of the Precipitation Processes in the Al-Mg-Si Alloy

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.723.27 ◽

2016 ◽

Vol 723 ◽

pp. 27-31

Author(s):

Ines Hamdi ◽

Zakaria Boumerzoug

Keyword(s):

Activation Energy ◽

Room Temperature ◽

Natural Aging ◽

Aging Effect ◽

Stable Phase ◽

Precipitation Process ◽

Precipitation Sequence ◽

Scanning Calorimetry ◽

Kissinger Model ◽

Precipitated Phases

The precipitation sequence of an Al-Mg-Si alloy depends on many parameters. In this study the natural aging effect on the activation energy of the precipitation sequence in the Al-Mg-Si alloy have been investigated by differential scanning calorimetry (DSC). The precipitation sequence of an Al-Mg-Si alloy has been established. The activation energy of the precipitation process was calculated using Kissinger model. The results obtained using this method showed a change in the activation energy for all precipitated phases. The activation energy of the metastable phases (β″ and β′) and the stable phase β formation in the Al-Mg-Si alloy aged at room temperature have been determined.

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The Simulation of Stress-Induced Phase Transition of L10 Re-Precipitation Based on Microscopic Phase-Field Model

Materials Science Forum ◽

10.4028/www.scientific.net/msf.689.226 ◽

2011 ◽

Vol 689 ◽

pp. 226-234

Author(s):

Yong Xin Wang ◽

Yong Biao Wang ◽

Zheng Chen ◽

Yan Li Lu

Keyword(s):

Phase Transition ◽

Induction Period ◽

Phase Field ◽

Field Model ◽

Large Range ◽

Phase Field Model ◽

Precipitation Process ◽

Phase Precipitation ◽

Microscopic Phase Field Model ◽

Precipitation Phase

It is common that the pre-precipitation phase with kinetics advantage is found during non-equilibrium transformation. The continuously changed stress in the transformation increases the complication of precipitation process. The stress induces Ll0pre-precipitation phase in Ni75-Al12.5-V12.5alloy is studied by microscope phase-field model in this paper. It is particularly show that Ll2phase precipitates directly without stress. There is no Ll0phase to be found in the disordered matrix. Oppositely, Ll0phase precipitates firstly with stress, and then it turns into Ll2phase. When stress is less, either or both above situations are observed. While stress is stronger, a large range of Ll0phase precipitates firstly. Then a part of it dissolves. The rest turns into Ll2phase. The precipitation of pre-precipitation phase accelerates the precipitation process. The larger the stress and the more Ll0phase precipitation, the longer it exists and the shorter the induction period is.

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A Liquid-Phase Precipitation Process for Selective Removal of Critical Inorganic Species from the Hanford Waste Streams

Environmental Engineering Science ◽

10.1089/ees.2006.23.296 ◽

2006 ◽

Vol 23 (2) ◽

pp. 296-308 ◽

Cited By ~ 1

Author(s):

M.S.H. Bader

Keyword(s):

Liquid Phase ◽

Selective Removal ◽

Precipitation Process ◽

Phase Precipitation ◽

Waste Streams ◽

Inorganic Species

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Phase-Field Simulation of δ-Ni2Si Precipitation in Cu-Ni-Si Alloys

Materials Science Forum ◽

10.4028/www.scientific.net/msf.689.184 ◽

2011 ◽

Vol 689 ◽

pp. 184-189

Author(s):

Yong Qiang Long ◽

Ping Liu ◽

Yong Liu

Keyword(s):

Phase Field ◽

Interfacial Energy ◽

Elastic Energy ◽

Phase Field Model ◽

Precipitation Process ◽

Phase Precipitation ◽

Coarsening Behavior ◽

Δ Phase ◽

Energy Anisotropy ◽

Precipitation Phase

The phase-field model is established for precipitation transformations in multi-component alloy, which incorporates the interfacial energy and elastic energy anisotropy. The mechanism of the precipitation phase transition is revealed by means of the simulation of δ-phase precipitation process in Cu-4.0at.%Ni-2.0at.%Si alloy, and furthermore, the δ-phase precipitation kinetics is built at the temperature of 450°C. Under the influence of both interfacial energy and elastic energy anisotropy, δ-Ni2Si is presented in disc-shaped precipitates. The simulation patterns show that when one precipitate hits another precipitate with a different orientation, it stops growing, consequently forming a “T”-shape precipitate configuration. When two precipitates with the same orientations grow and hit each other, they connect or coarsen only if the spacing between the precipitates is very small. Therefore, the coarsening behavior of disc-shaped precipitate should be completely different from that of spherical precipitates.

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Electron microscopical investigations of hexagonal phase precipitation in Zn12 wt% Al1 wt% Cu and Zn27 wt% Al2 wt% Cu alloys

Acta Metallurgica et Materialia ◽

10.1016/0956-7151(91)90187-6 ◽

1991 ◽

Vol 39 (9) ◽

pp. 2177-2182 ◽

Cited By ~ 4

Author(s):

P. Rachev ◽

L. Terziev ◽

J. Lecomte-Beckers ◽

J. Wegria

Keyword(s):

Hexagonal Phase ◽

Phase Precipitation ◽

Cu Alloys ◽

Electron Microscopical ◽

Cu And Zn

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Capturing the influence of geometric variations on permeability using a numerical permeability prediction tool

Journal of Reinforced Plastics and Composites ◽

10.1177/0731684416669249 ◽

2016 ◽

Vol 35 (24) ◽

pp. 1802-1813 ◽

Cited By ~ 10

Author(s):

Elinor E Swery ◽

Tom Allen ◽

Piaras Kelly

Keyword(s):

Single Unit ◽

Close Agreement ◽

Single Layer ◽

Prediction Tool ◽

Number Of Layers ◽

Unit Cells ◽

Modelling Techniques ◽

Woven Textile ◽

Automated Tool ◽

Textile Modelling

An automated tool has been developed for generation of permeability predictions for multi-layered unit cells utilising textile modelling techniques. This tool has been used to predict the permeability tensor of a woven textile. Single-layer predictions were carried out and the predicted permeabilities obtained were in close agreement to the permeability behaviour captured experimentally. The tool was used to capture the effects of textile variability on its permeability, isolating the influence of individual parameters. A complete textile sample was also analysed, predicting its permeability map. The concept of estimating the permeability of a textile with variability using an average single unit cell was explored. The prediction tool was also used to study the effect of preform structure on its permeability, including consideration of the number of layers, ply shift and applied compaction.

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Precipitation Process in a Cu-Ni-Be Alloy

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.172-174.432 ◽

2011 ◽

Vol 172-174 ◽

pp. 432-436 ◽

Cited By ~ 9

Author(s):

Chihiro Watanabe ◽

Ryoichi Monzen

Keyword(s):

Electron Microscopy ◽

Precipitation Process ◽

Average Thickness ◽

Precipitation Sequence ◽

Transmission Electron ◽

The Matrix ◽

Precipitated Phases ◽

Kinetics Of ◽

Ledge Mechanism ◽

Habit Planes

The precipitation process in an aged Cu-1.9wt%Ni-0.3wt%Be alloy has been examined by high-resolution transmission electron microscopy. The precipitation sequence found is: Guinier- Preston (G.P.) zones → γ'' → γ' → stable γ. The disk-shaped G.P. zones and the disk-shaped γ'', γ' and γ precipitated phases are composed of monolayers of Be atoms on {100}αof the Cu matrix and alternative Be and Ni matrix layers parallel to {100}α. The γ'' phases consisting of two to eight Be-layers has a body-centered tetragonal (bct) lattice witha=b=0.24 nm andc=0.28 nm. The γ' or γ phase is bct witha=b=0.24 nm andc=0.26 nm ora=b=0.26 nm andc=0.27 nm. The γ'', γ' or γ phase aligns with the matrix according to the Bain orientation relationship. The growth kinetics of disk-shaped γ precipitates on aging at 500°C has been also investigated. The {001}αhabit planes of the γ precipitates migrate by a ledge mechanism. The average thickness of the γ disks increases with aging timetast1/2. An analysis of experimental data using a kinetic model yields the diffusivity of solute in the Cu matrix, which is in agreement with the reported diffusivity of Ni in Cu.

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The Dual Nature of Precipitates in Al-Mg-Si Alloys

Materials Science Forum ◽

10.4028/www.scientific.net/msf.638-642.390 ◽

2010 ◽

Vol 638-642 ◽

pp. 390-395 ◽

Cited By ~ 15

Author(s):

Sigmund J. Andersen ◽

Calin D. Marioara ◽

René Vissers ◽

Malin Torsæter ◽

Ruben Bjørge ◽

...

Keyword(s):

Material Properties ◽

Mirror Plane ◽

Precipitation Process ◽

Dual Nature ◽

Cu Alloys ◽

Main Plane ◽

Super Cell ◽

The Matrix ◽

Hexagonal Arrangement ◽

Al Matrix

Precipitates in Al-Mg-Si-(Cu) alloys all contain a similar hexagonal arrangement of Si-atoms. Precipitates come and go but their inner Si ordering appears to vary little throughout the precipitation process. In order to improve understanding of precipitation and the related material properties, it is becoming increasingly clear that this includes a good understanding of the hexagonal Si-network, its relation to the precipitates and the Al matrix. Previous studies have revealed that adding Cu atoms to the ternary system, causes the Si network to twist slightly in the matrix about its hexagonal axis, favoring different precipitates. Here we investigate these two rotations. It is shown they can be viewed as a mirror of the network itself about a {310} Al plane. Since precipitates are coherent, the Si-network with its triangular arrangements of Si must also match a fourfold arrangement of Al on the {100} planes. Sets of Al lattice positions exist which can approximate the tree-fold Si symmetry, according to the experimentally observed orientations, and one or more large super-cells can be found having near fit in both lattices. The mirror plane is a main plane in one such super-cell. We show that the mirror leaves every seventh node of the network unchanged, thus defining a smaller hexagonal super-cell in the network, similar to the B’ or Q’/Q phase, where corners are invariant, but where the Si contents is flipped.

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