Microstructural evolution in aluminium alloy 7050 during processing

Robson, James

doi:10.1016/j.msea.2004.05.006

Cited by 177 publications

(43 citation statements)

References 11 publications

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“…Figure 4 demonstrates that the XTM technique can provide detailed microstructural information based on the density of different phases of the alloy. Air or void spaces appear in black, the aluminum matrix is represented by gray, while eutectic phases that contain heavier elements, for instance Al 2 CuMg (S-phase), Al 2 Mg 3 Zn 3 (T-phase) and MgZn 2 (M-phase), [17,18] appear as lighter gray.…”

Section: A Mechanical Responsementioning

confidence: 99%

Formation of Hot Tear Under Controlled Solidification Conditions

Subroto

Miroux

Bouffier

et al. 2014

Metall Mater Trans A

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Aluminum alloy 7050 is known for its superior mechanical properties, and thus finds its application in aerospace industry. Vertical direct-chill (DC) casting process is typically employed for producing such an alloy. Despite its advantages, AA7050 is considered as a ''hardto-cast'' alloy because of its propensity to cold cracking. This type of cracks occurs catastrophically and is difficult to predict. Previous research suggested that such a crack could be initiated by undeveloped hot tears (microscopic hot tear) formed during the DC casting process if they reach a certain critical size. However, validation of such a hypothesis has not been done yet. Therefore, a method to produce a hot tear with a controlled size is needed as part of the verification studies. In the current study, we demonstrate a method that has a potential to control the size of the created hot tear in a small-scale solidification process. We found that by changing two variables, cooling rate and displacement compensation rate, the size of the hot tear during solidification can be modified in a controlled way. An X-ray microtomography characterization technique is utilized to quantify the created hot tear. We suggest that feeding and strain rate during DC casting are more important compared with the exerted force on the sample for the formation of a hot tear. In addition, we show that there are four different domains of hot-tear development in the explored experimental window-compression, microscopic hot tear, macroscopic hot tear, and failure. The samples produced in the current study will be used for subsequent experiments that simulate cold-cracking conditions to confirm the earlier proposed model.

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Section: A Mechanical Responsementioning

confidence: 99%

Formation of Hot Tear Under Controlled Solidification Conditions

Subroto

Miroux

Bouffier

et al. 2014

Metall Mater Trans A

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“…Although the KWN model has been successfully applied to different aluminium alloys (Myhr et al, 2001;Robson, 2004a), there are no reports of application to casting aluminium alloys. The present modelling work is the first time that KWN model has been applied to the casting aluminium alloys A356 and A357 for different ageing temperatures and compared with the experimental data.…”

Section: Application To the Casting Aluminium Alloysmentioning

confidence: 99%

“…And then a strength model is used to evaluate the resulting change in hardness or yield strength at room temperature by taking into account contributions from lattice resistance, solid solution hardening and precipitation hardening. Though the KWN model has been developed for a few decades and successfully applied to a number of aluminium alloy systems, such as 2xxx, 6xxx and 7xxx (Myhr & Grong, 2000;Myhr et al, 2001;Robson, 2004a;Robson, 2004b) , however, most of modelling work has been focused on the wrought aluminium alloys and none modelling work has been applied to the casting aluminium alloys. In the present work, the KWN model has been for the first time applied to the casting aluminium alloys A356 and A357.…”

Section: Introductionmentioning

confidence: 99%

Modelling of Precipitation Hardening in Casting Aluminium Alloys

Ferguson

2009

MSF

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Precipitation hardening, or aging hardening, is one of the most widely adopted techniques for strengthening of aluminium alloys. During the precipitation process, three major mechanisms are involved: i.e. nucleation, growth and coarsening. Kampmann and Wagner have developed a powerful and flexible numerical approach (KWN model) for dealing with concomitant nucleation, growth and coarsening and thus capable of predicting the full evolution of the particle size distribution. KWN model has been successfully applied to a number of aluminium alloy systems, such as 2xxx, 6xxx and 7xxx. However, most of these modelling works were focused on the wrought aluminium alloys, few had applied to the casting aluminium alloys. In the present modelling work, the microstructure evolution is modeled based on the KWN model and then a strength model based on the well established dislocation theory is used to evaluate the resulting change in hardness or yield strength at room temperature. Then the modelling is applied to casting aluminium alloys A356 and A357. And the modelling results are validated by comparing with own experimental results and the results obtained from the open literature.

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“…In the early 21 st century, some wrought aluminum alloys with very _______________________ high Zn content higher than 8.4wt%, such as AA7136, AA7095, AA7056, were registered as international designation successively, aims to replace the ultra-high strength AA7055 alloy for aerospace applications [5,6]. It is well known that homogenization process is very important for high alloying elements content 7xxx series aluminum alloys, because the microsegreation of Zn,Cu, and Mg elements and coarse intermetallic particles results in poor comprehensive properties [7,8]. Furthermore, the two-stage homogenization is widely known as not only dissolving the intermetallic particles into the aluminum matrix, but also controlling ideally the precipitation of Al 3 Zr dispersoids in the wrought 7xxx series aluminum alloys with addition of zirconium [6,7].…”

Section: Introductionmentioning

confidence: 99%

“…It is well known that homogenization process is very important for high alloying elements content 7xxx series aluminum alloys, because the microsegreation of Zn,Cu, and Mg elements and coarse intermetallic particles results in poor comprehensive properties [7,8]. Furthermore, the two-stage homogenization is widely known as not only dissolving the intermetallic particles into the aluminum matrix, but also controlling ideally the precipitation of Al 3 Zr dispersoids in the wrought 7xxx series aluminum alloys with addition of zirconium [6,7]. However, the study on microstructure in as-cast Al-ZnMg-Cu aluminum alloy with high Zn-containing (>9wt%) and its evolution during homogenization is still very limited.…”

Section: Introductionmentioning

confidence: 99%

Investigation on As-Cast Microstructure in a high Zn-containing Al-Zn-Mg-Cu-Zr alloy and Its Evolution during Two-stage Homogenization

Fan¹,

Li²,

Li³

et al. 2017

dtetr

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In this study, the as-cast microstructure of a high Zn-containing Al-Zn-Mg-CuZr alloy and its evolution during two-stage homogenization were investigated by means of optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and differential scanning calorimetry (DSC) analysis. The analysis shows the eutectic structures in as-cast the alloy were identified as α(Al) / Mg(Zn,Cu,Al) 2 , and also some Al 2 CuMg, Al 2 Cu and Fe-rich phases formed in the eutectic structures during solidification. With the prolonging of the second stage homogenization time, S(Al 2 CuMg), θ(Al 2 Cu) and Mg(Zn,Cu,Al) 2 phases orderly dissolved into the matrix, and the insoluble Fe-rich phases exist in all five as-homogenized schemes in this study, but Zn and Mg elements changes detected in the these particles during the two stage homogenization.

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Microstructural evolution in aluminium alloy 7050 during processing

Cited by 177 publications

References 11 publications

Formation of Hot Tear Under Controlled Solidification Conditions

Formation of Hot Tear Under Controlled Solidification Conditions

Modelling of Precipitation Hardening in Casting Aluminium Alloys

Investigation on As-Cast Microstructure in a high Zn-containing Al-Zn-Mg-Cu-Zr alloy and Its Evolution during Two-stage Homogenization

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