The structural and compositional evolution of precipitates in Al-Mg-Si-Cu alloy

Ding, Lipeng; Jia, Zhihong; Nie, Jian–Feng; Weng, Yaoyao; Cao, Lingfei; Chen, Houwen; Wu, Xiaozhi; Liu, Qing

doi:10.1016/j.actamat.2017.12.036

Cited by 238 publications

(113 citation statements)

References 36 publications

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“…Several precipitates at this condition showed the same tendency, with a predominantly Al-Mg-Si containing β /U2 interior, and Cu-enrichment, as well as randomly positioned sub-units of Cucontaining phases at the precipitate interface. This is similar to earlier results [26,43], showing β /disordered precipitates at under-aged and peak hardness conditions for alloys with higher Cu content. The positions of Cu enriched columns in the βphase for the 3 h and 24 h conditions seem to agree with the findings of Li et al [44], which found that Cu incompletely substitutes for Mg 1 and Si 3 (here, Al) columns.…”

Section: Sped Data Analysissupporting

confidence: 92%

The evolution of precipitate crystal structures in an Al-Mg-Si(-Cu) alloy studied by a combined HAADF-STEM and SPED approach

Sunde

Marioara

Holmestad

2018

Materials Characterization

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This work presents a detailed investigation into the effect of a low Cu addition (0.01 at.%) on precipitation in an Al-0.80Mg-0.85Si alloy during ageing. The precipitate crystal structures were assessed by scanning transmission electron microscopy combined with a novel scanning precession electron diffraction approach, which includes machine learning. The combination of techniques enabled evaluation of the atomic arrangement within individual precipitates, as well as an improved estimate of precipitate phase fractions at each ageing condition, through analysis of a statistically significant number of precipitates. Based on the obtained results, the total amount of solute atoms locked inside precipitates could be approximated. It was shown that even with a Cu content close to impurity levels, the Al-Mg-Si system precipitation was significantly affected with overageing. The principal change was due to a gradually increasing phase fraction of the Cu-containing Q -phase, which eventually was seen to dominate the precipitate structures. The structural overtake could be explained based on a continuous formation of the thermally stable Q -phase, with Cu atomic columns incorporating less Cu than what could potentially be accommodated.

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Section: Sped Data Analysissupporting

confidence: 92%

The evolution of precipitate crystal structures in an Al-Mg-Si(-Cu) alloy studied by a combined HAADF-STEM and SPED approach

Sunde

Marioara

Holmestad

2018

Materials Characterization

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“…Ag atoms were found to segregate at the GP zone/α-Al interface by the replacement of Al atom in FCC matrix, and no Ag atom was found in the interior of GP zone. This phenomenon is different from the Cu addition, in which Cu could incorporate into the interior of GP-zone and form its local symmetry, Cu sub-unit cluster, in Al-Mg-Si-Cu alloys [26]. More images of GP zones formed in the peak-aged A2 alloy are presented in Supplementary Fig.…”

Section: Peak-aged Microstructurementioning

confidence: 92%

“…Addition of Cu or Ag is known to be effective in increasing the precipitation strengthening for Al-Mg-Si alloys [17][18][19][20]. Cu suppresses the precipitation of β″ phase and facilitates the formation of Cu-containing phases, such as Q′, QP1, QP2, C and Q, thus changes the precipitation sequence of Al-Mg-Si alloys [21][22][23][24][25][26].…”

Section: Introductionmentioning

confidence: 99%

Effect of Ag addition on the precipitation evolution and interfacial segregation for Al–Mg–Si alloy

et al. 2019

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The effect of Ag addition on the precipitation evolution and interfacial segregation for Al-Mg-Si alloys was systematically investigated by atomic resolution high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), atom probe tomography (APT) and density functional theory (DFT) calculation. At the early aging stage, Ag atoms could enter clusters and refine the distribution of these clusters. Then, Ag atoms preferentially segregate at the GP zone/α-Al and β"/α-Al interfaces at the peak aging stage by the replacement of Al atoms in FCC matrix. With prolonging aging time, Ag atoms generally incorporate into the interior of β" precipitate, facilitating the formation of QP lattice (a hexagonal network of Si atomic columns) and the local symmetry substructures, Ag sub-unit (1) and Ag sub-unit (2). At the over-aged stage, the Ag sub-unit (1) and Ag sub-unit (2) could transform to the β′Ag (i.e. β′Ag1 and β′Ag2.) and Q′Ag unit cells, respectively. All the precipitates at the over-aging stage have a composite and disordered structure due to the coexistence of different unit cells (β′Ag1, β′Ag2, Q′Ag and β′) and the non-periodic arrangement of Ag atoms within the precipitate. In the equilibrium stage, the incorporated Ag atoms in the precipitates release into the α-Al matrix as solute atoms or form Ag particles. In general, Ag atoms undergo a process of "segregate at the precipitate/matrix interface → incorporate into the interior of precipitate → release into the α-Al matrix" during the precipitation for Al-Mg-Si-Ag alloys. Besides, Ag segregation is found at the interfaces of almost all metastable phases (including GP zone, β″, β′/ β′Ag phase) in Al-Mg-Si-Ag alloys. The Ag segregation at the β′/α-Al interface could increase the length/diameter ratio of β′ phase and thus promote the additional strengthening potential of these alloys. These findings provide a new route for precipitation hardening by promoting the nucleation and morphology evolution of precipitates.

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“…The resulting phases after casting, like Al 5 FeSi, are well-known and investigated by several authors [21][22][23]. The process of precipitation and the hardening phases during NA and AA have been investigated by Mondolfo [24] and other authors [25][26][27][28][29]. To analyze the different phases in detail, using another etching and a TEM is irreplaceable for further investigations.…”

Section: Discussionmentioning

confidence: 99%

Influence of Short-Term Heat Treatment on the Mechanical Properties of Al–Mg–Si Profiles

Kernebeck

Weber

2018

Metals

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Aluminum profiles-for instance, profiles made of precipitation-hardenable alloys-are increasingly used for decorative details in the automotive industry. Typically, after hot extrusion and at least two to three days of natural aging (NA), the aluminum profiles are artificially aged. A commercial EN AW-6060 alloy of high purity was used for this investigation. Tensile tests were used as the main measurement method. This article focuses on the effect of short-term heat treatment on the point in time at which a significant increase of the ultimate tensile strength (UTS) during NA can be measured. Short-term heat treatment is shown to delay this point in time by almost four days, but it increases the variation of UTS. A heterogeneous temperature profile during short-term heat treatment was identified as one reason for this result. Finally, a strategy for minimizing variations in mechanical properties of artificially-aged aluminum alloys was developed, based on the experimental results of this study.

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The structural and compositional evolution of precipitates in Al-Mg-Si-Cu alloy

Cited by 238 publications

References 36 publications

The evolution of precipitate crystal structures in an Al-Mg-Si(-Cu) alloy studied by a combined HAADF-STEM and SPED approach

The evolution of precipitate crystal structures in an Al-Mg-Si(-Cu) alloy studied by a combined HAADF-STEM and SPED approach

Effect of Ag addition on the precipitation evolution and interfacial segregation for Al–Mg–Si alloy

Influence of Short-Term Heat Treatment on the Mechanical Properties of Al–Mg–Si Profiles

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