Clustering in Age‐Hardenable Aluminum Alloys

Dumitraschkewitz, Phillip; Gerstl, Stephan S.A.; Stephenson, Leigh T.; Uggowitzer, Peter J.; Pogatscher, Stefan

doi:10.1002/adem.201800255

Cited by 80 publications

(37 citation statements)

References 140 publications

(274 reference statements)

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“…maximum separation or other related). When affected by trajectory aberrations, the identification of clusters based on a threshold of distance or composition [3] is hence likely to fail to assess which atoms physically belong to clusters. While several studies have investigated the effect of an imperfect reconstruction (by adding random Gaussian noise to a synthetic APT volume) on cluster identification methods, most concluded that it did not yield too strong an effect on the clusters on the basis of a strongly underestimated effective spatial The values that we report here seem to correspond to the worst case scenario of these studies, when problems start to arise.…”

Section: Discussionmentioning

confidence: 99%

“…precipitates, in the nanometer-size range and below [1,2]. This is particularly true for solute clusters [3]. The detailed analysis of the composition of these precipitates and clusters is of high relevance to studies of the early stages of nucleation of new phases, which control both the physical properties of materials and the further evolution of the microstructure.…”

Section: Introductionmentioning

confidence: 99%

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Metrology of small particles and solute clusters by atom probe tomography

2020

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Atom probe tomography (APT) is routinely used for analyzing property-enhancing particles in the nanometer-size range and below, and plays a prominent role in the analysis of solute clusters. However, the question of how well these small particles are measured has never been addressed because of a lack of a reliable benchmark. Here, to address this critical gap, we use an approach that allows direct comparison of APT and small-angle (X-Ray) scattering (SA(X)S) performed on the same material. We introduce the notion of an effective spatial resolution for the analysis of particles, which, importantly in this context, is very different than the technique's inherent spatial resolution. This effective resolution is highly specific to the system being considered, as well as the analysis conditions. There is no hard limit below which the technique will fail, but for particles with a radius of order of 2σ = 1 nm, i.e. 250 atoms, cannot be accurately measured, even though the particles are detected. This thorough metrological assessment of APT in the analysis of particles allows us to discuss the pulse spread function of the technique and the physics underpinning its limits. We conclude that great care should be taken when analysing solute clusters by APT, in particular when reporting particle size and composition.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Metrology of small particles and solute clusters by atom probe tomography

2020

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“…This could be explained by the clusters formed upon pre-ageing, which may stabilize the dislocations structure via coherency strengthening effects [34], and thus restrain recovery. The clusters formed upon pre-ageing represent greater obstacles to dislocations than those formed upon natural ageing, and, more importantly, they are stable and hardly dissolve upon artificial ageing [35].…”

Section: Resultsmentioning

confidence: 99%

Ageing Behaviour of Al–Mg–Si Alloys After Cryogenic and Room Temperature Deformation

Gruber

Grabner

Fragner³

et al. 2020

Materials

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The aim of this study is to investigate the effects of cryogenic and room temperature pre-deformation on subsequent artificial ageing of Al–Mg–Si alloys. Naturally aged and pre-aged samples were strained to 5%, 10% and 20% at RT (25 °C) and under liquid nitrogen, and artificially aged at 185 °C. Pre-deformation generally increases ageing kinetics for both the naturally aged and pre-aged alloys, which increase in proportion to the degree of pre-deformation, and which are slightly more pronounced for the cryogenic condition. The peak strength is constant, except for when a low degree of pre-deformation is used, in which case it is slightly reduced. Cryogenically deformed samples show an increased strength and hardness, compared to samples pre-deformed at RT, when subjected to an equal magnitude of strain. This difference is reduced during artificial ageing. Synchrotron measurements reveal that this behaviour can be linked to the greater dislocation density, which is not completely recovered even after prolonged ageing at 185 °C.

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“…In EN-AW-6061, the effect of 100 at.-ppm of Sn vanishes when air cooling is applied (Figure 3b). Note that the higher Si-content in EN-AW-6016 may lead to a significant acceleration of natural aging in general [16,23,29].…”

Section: Discussionmentioning

confidence: 99%

“…The crucial property of clusters, in terms of transformation in the course of AA, is claimed to be the Mg/Si ratio. While measurements show a balanced ratio of about one for PA-treatments, clusters tend to follow the overall composition of the alloy after NA [12,13,14,15,16]. Besides “conventional” pre-aging for several hours, applying a spike as a short-term treatment at high temperatures (180 °C and 200 °C) also shows promising results [6,17,18].…”

Section: Introductionmentioning

confidence: 99%

Effect of Thermal Treatments on Sn-Alloyed Al-Mg-Si Alloys

et al. 2019

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Sn-alloying, by deploying comparatively high vacancy binding energy, mitigates the undesired natural aging behavior of 6xxx-alloys. Targeted selection of pre-aging parameters can have a positive influence on natural aging and paint-bake performance. In this study, we aimed to combine the two approaches of Sn-alloying and pre-aging. Our results indicate that alloys modified with 100 at.-ppm Sn require altered heat treatment. In terms of solution aging and quenching, we show that the cooling rate needed depends on the types of alloy. The rate must be adapted, according to the number of intermetallic particles, to guarantee a sufficiently high level of Sn atoms in solid solution. The rather high number of intermetallic phases in alloy EN-AW-6061 means that it requires fast quenching, while the comparatively low number of precipitate-forming elements in alloy EN-AW-6016 makes it less sensitive to quenching variations. We also show that Sn reduces pre-aging kinetics. The optimal pre-aging temperature and time were consequently found to increase when Sn is added. We also studied the effect of adding a further thermal spike to the usual long-term pre-aging, at different positions within the processing route. The results we present are discussed based on a simulation of vacancy evolution in the alloy when subjected to these treatments.

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Clustering in Age‐Hardenable Aluminum Alloys

Cited by 80 publications

References 140 publications

Metrology of small particles and solute clusters by atom probe tomography

Metrology of small particles and solute clusters by atom probe tomography

Ageing Behaviour of Al–Mg–Si Alloys After Cryogenic and Room Temperature Deformation

Effect of Thermal Treatments on Sn-Alloyed Al-Mg-Si Alloys

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