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Starink, M.J.

doi:10.1023/a:1017974517877

Cited by 162 publications

(98 citation statements)

References 51 publications

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“…According to applicable transformation theory [39] n = 2½ will occur for any reaction that is dominated by steady nucleation [40], with few or no nuclei present at the start of the analysis, followed by diffusion-controlled growth [40]. In fact, this agrees very well with our χ 2 test on the frequency distribution of Mg atoms obtained from 3DAP analysis of our alloys which shows that initially, shortly after quenching, the Mg atoms are distributed nearly perfectly randomly and on roomtemperature ageing the distribution becomes clustered (Fig.…”

Section: Model For Reaction Kinetics and Hardeningmentioning

confidence: 99%

Reply to the comments on “Room-temperature precipitation in quenched Al–Cu–Mg alloys: a model for the reaction kinetics and yield-strength development”

Starink

Cerezo

Yan

et al. 2006

Philosophical Magazine Letters

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Our recent work on Al-Cu-Mg -based alloys with Cu:Mg ratio close to unity showed that the rapid hardening at room temperature and the substantial heat evolution arise from the formation of Cu-Mg co-clusters. Here, it is shown that the measured enthalpy of formation of clusters (~0.3eV per Mg atom) is in reasonable agreement with expectations based on the similarity with Mg-vacancy clusters. The origin of the term GPB zones, as applied to the rapid hardening in Al-Cu-Mg -based alloys, is investigated. It is shown that current knowledge on the nanostucture and microstructure development during rapid hardening can be described without recourse to this alloy-specific term. Analysis of the kinetics of Cu-Mg co-cluster formation by DSC indicates that the formation of CuMg co-clusters during a fast water quench can be sufficiently suppressed to cause substantial nucleation of co-clusters to occur in subsequent natural ageing and artificial ageing at low temperatures.In this reply to [1], which contains some comments on our paper [2], we would like to discuss a number of issues pertinent to points raised by Zahra et al. in the course of their paper. Before we deal with these we first want to note that much of [1] is taken up by a literature review and by a review of calorimetry data, which do not contradict our work. We will not comment on this but we do need to stress that the final interpretation by Zahra et al.[1] "[..] plate-like GPB zones which nucleate on clusters of irregular shape are responsible for the first hardening stage" is inconsistent with our three-dimensional atom probe (3DAP), differential scanning calorimetry (DSC) and hardness data on the two alloys we studied (Al-1.2Cu-1.2Mg and the Al-1.9Cu-1.6Mg (at%)): our 3DAP data shows that neither of these alloys contain substantial numbers of platelet or rod-like structures such as GPB zones during several days ageing at room temperature, whilst the hardness increase and heat evolution is completed within about one day. We will show that all the data and theoretical considerations expressed in [1], as well as data in papers cited in [1], are fully consistent with our conclusions. Specifically we need to note that nowhere in [1], or in any of the papers cited therein, is any nano/microstructural data presented that show platelet or rod-shaped GPB zones within Al-Cu-Mg alloy samples with compositions and heat treatments near the ones we have studied. We believe that there is no conclusive microstructural data having the necessary resolution on Al-Cu-Mg alloys with both Cu and Mg contents in excess of 1at%, heat treated to times up to 5 ×

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Section: Model For Reaction Kinetics and Hardeningmentioning

confidence: 99%

Reply to the comments on “Room-temperature precipitation in quenched Al–Cu–Mg alloys: a model for the reaction kinetics and yield-strength development”

Starink

Cerezo

Yan

et al. 2006

Philosophical Magazine Letters

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“…[11] leads to the Johnson-Mehl-Avrami-Kolmogorov (JMAK equation), if n = 2 to the Austin-Rickett equation. [36,37] The relation used between f and x e is [16,38,39] df dx e ¼ ð1 À fÞ n ½11…”

Section: Growth Modementioning

confidence: 99%

“…[36,39] Upon integration Eq. [11] becomes *Fitting the kinetics model to the experimental data upon incorporation of a ''thickening'' growth mode (additional to the ''lengthening'' growth mode) by dislocation climb did not alter the results significantly; dislocation climb is very much slower than dislocation glide.…”

Section: Growth Modementioning

confidence: 99%

Kinetics of the fcc → hcp Phase Transformation in Cu-Ge Solid Solutions Upon Isothermal Aging

Polatidis

Zotov

Bischoff

et al. 2017

Metall Mater Trans A

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The kinetics of the f-phase formation from a supersaturated a-Cu(Ge) solid solution (i.e., transformation from the fcc crystal structure to the hcp crystal structure) containing 10.8 at. pct Ge [at isothermal temperatures of 573 K, 613 K, and 653 K (300°C, 340°C, and 380°C)] were studied by X-ray diffraction (XRD) for phase fraction determination. Both in situ and ex situ annealing experiments were performed. The transformation kinetics were modeled on the basis of a versatile modular model. The transformation kinetics complied with a site-saturation nucleation mode and strongly anisotropic interface-controlled growth mode in association with a corresponding impingement mode: diffusion of Ge (towards the stacking faults, SFs) does not control the transformation rate. Transmission electron microscopy (TEM) investigations showed that segregation of Ge at the stacking faults (SFs) takes place (relatively fast) prior to the structural transformation (fcc fi hcp).

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“…[25,8,45], and experimentally verified for a number of precipitation reactions in heat treatable Al based alloys [46,47,48];…”

Section: Heat Treatment -Microstructure -Strength Modelmentioning

confidence: 99%

“…The transformed fraction of precipitates during ageing can be described by the Starink-Zahra (SZ) model for nucleation and growth [45][46][47][48]:…”

Section: Acknowledgementsmentioning

confidence: 99%

VPPA welds of Al-2024 alloys: Analysis and modelling of local microstructure and strength

Wang

Lefebvre

Yan

et al. 2006

Materials Science and Engineering: A

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The microstructural features of variable polarity plasma arc welded Al-Cu-Mg 2024-T351 with 2319 filler have been studied by TEM, SEM and DSC. Fusion zone, partial melting zone, resolutionising zone, overageing (for S phase), peak ageing (for S phase) and under ageing zones (for S phase) have been identified. The Ω phase has been observed between re-solutionising zone and peak ageing zone. The hardness profile contains two peaks. The microstructure development, and resulting hardness and yield strength profiles are modelled using a model which combines primary precipitation, resolution, partial/full melting and resolidification (Scheil type) and reprecipitation, in a two precipitate -two mechanism approach. Hardness profiles and microstructures are accurately predicted. The hardness peak in the re-solutionising zone is due to re-solutionising and subsequent Cu-Mg co-cluster formation; and the second hardness peak is caused by S phase strengthening.

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Untitled

Cited by 162 publications

References 51 publications

Reply to the comments on “Room-temperature precipitation in quenched Al–Cu–Mg alloys: a model for the reaction kinetics and yield-strength development”

Reply to the comments on “Room-temperature precipitation in quenched Al–Cu–Mg alloys: a model for the reaction kinetics and yield-strength development”

Kinetics of the fcc → hcp Phase Transformation in Cu-Ge Solid Solutions Upon Isothermal Aging

VPPA welds of Al-2024 alloys: Analysis and modelling of local microstructure and strength

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