Evolution of eutectic structures in Al-Zn-Mg-Cu alloys during heat treatment

Fan, Xing; Jiang, Daming; Meng, Qingchang; Zhang, Baoyou; Wang, Tao

doi:10.1016/s1003-6326(06)60101-5

Cited by 100 publications

(46 citation statements)

References 15 publications

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“…This illustrates that Fe-rich secondary particles cannot be dissolved into the matrix for the semi-solid treatment conditions used in the present study. Previous work reported that the melting temperature of η-phase in 7xxx alloys is 475-480˝C [26,27]. This is fairly well correlated with the first peak in the DSC curve of the starting material with an enthalpy of 2.7 J/g in Figure 1.…”

Section: Phase Evolution and Alloying Element Distribution During Parsupporting

confidence: 74%

“…This mechanism is less effective in particle growth but has a great influence on the spheroidization of solid grains. In contrast, the coalescence mechanism which needs shorter holding times and a small amount of liquid fractions, is more effective in grain growth and has a minor effect on the spheroidization process [25][26][27].…”

Section: Kinetics Of the Microstructural Evolution During Partial Remmentioning

confidence: 99%

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Phase Evolution and Mechanical Behavior of the Semi-Solid SIMA Processed 7075 Aluminum Alloy

Binesh

Aghaie-Khafri

2016

Metals

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Microstructural and mechanical behaviors of semi-solid 7075 aluminum alloy were investigated during semi-solid processing. The strain induced melt activation (SIMA) process consisted of applying uniaxial compression strain at ambient temperature and subsequent semi-solid treatment at 600-620˝C for 5-35 min. Microstructures were characterized by scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD). During the isothermal heating, intermetallic precipitates were gradually dissolved through the phase transformations of α-Al + η (MgZn 2 ) Ñ liquid phase (L) and then α-Al + Al 2 CuMg (S) + Mg 2 Si Ñ liquid phase (L). However, Fe-rich precipitates appeared mainly as square particles at the grain boundaries at low heating temperatures. Cu and Si were enriched at the grain boundaries during the isothermal treatment while a significant depletion of Mg was also observed at the grain boundaries. The mechanical behavior of different SIMA processed samples in the semi-solid state were investigated by means of hot compression tests. The results indicated that the SIMA processed sample with near equiaxed microstructure exhibits the highest flow resistance during thixoforming which significantly decreases in the case of samples with globular microstructures. This was justified based on the governing deformation mechanisms for different thixoformed microstructures.

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Section: Phase Evolution and Alloying Element Distribution During Parsupporting

confidence: 74%

Section: Kinetics Of the Microstructural Evolution During Partial Remmentioning

confidence: 99%

Phase Evolution and Mechanical Behavior of the Semi-Solid SIMA Processed 7075 Aluminum Alloy

Binesh

Aghaie-Khafri

2016

Metals

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“…These are mainly; T-AlMg 4 Zn 11 , S-Al 2 CuMg, and η-MgZn 2 phases. Generally the accepted precipitates' formation sequence for the 7000 series alloys are as reported in 27,28 . Metastable the h′phase stands as the main strengthening precipitate for these alloys.…”

Section: Resultsmentioning

confidence: 99%

The Role of cobalt and nickel intermetallic phases on the mechanical properties and microstructure evolution of Al-Zn-Mg-Cu alloys

2014

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In this study, the effects of cobalt and nickel additions on microstructure evolution and mechanical properties of Al-Zn-Mg-Cu alloys produced by chill casting process were investigated. Al-Zn-MgCu aluminum alloys containing Ni and Co additives were homogenized at different heat treatment conditions, aged at 120°C for 24 h, and retrogressed at 180°C for 30 min then re-aged at 120°C for 24h.Comparison of the ultimate tensile strength of the Al-Zn-Mg-Cu base alloy underwent RRA temper process with that of the base alloy underwent a similar heat treatment process after the addition of 0.5 wt. % Ni and 0.5 wt. % Co showed that the gains of tensile strengths of the orders of 100 MPa and 135 MPa were attained respectively. These improvements are attributed to phase dispersion particles of the formation of Ni and Co-rich such as and Co intermetallic dispersoids retarded the grain growth, led to grain refinement and precipitation hardening and resulted in further strengthening of the Al alloy. Microstructure characterization of the alloys was carried out using optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD).

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“…As is well known, Peak II is attributed to the melting of the (Al + r) eutectic, [28] more intrinsically this endothermic reaction can be regarded as the gradual dissolution of r phase with heating. However, there is no clear explanation about the reaction related to Peak I in the existing literature.…”

Section: A Phase Components and Solidification Paths Of The As-cast mentioning

confidence: 93%

Solidification Paths and Phase Components at High Temperatures of High-Zn Al-Zn-Mg-Cu Alloys with Different Mg and Cu Contents

Shu

Hou

Liu

et al. 2015

Metall Mater Trans A

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Studies were carried out systematically on a series of Al-8.5 wt pct Zn-xMg-yCu alloys (x is about 1.5, 2.0, and 2.5 wt pct, and y is about 1.5, 2.0, 2.5, and 2.9 wt pct). The effects of alloying elements Mg and Cu on the microstructures of as-cast and homogenized alloys were investigated using the computational/experimental approach. It shows that Mg(Zn,Al,Cu) 2 (r) phase can exist in all the as-cast alloys without any observable Mg 32 (Al,Zn) 49 /Al 2 Mg 3 Zn 3 (T) or Al 2 CuMg (S) phase, whereas Al 2 Cu (h) phase is prone to exist in the alloys with low Mg and high Cu contents. Thermodynamic calculation shows that the real solidification paths of the designed alloys fall in between the Scheil and the equilibrium conditions, and close to the former. After the long-time homogenization [733 K (460°C)/168 hours] and the two-step homogenization [733 K (460°C)/24 hours + 748 K (475°C)/24 hours], the phase components of the designed alloys are generally consistent with the calculated phase diagrams. At 733 K (460°C), the phase components in the thermodynamic equilibrium state are greatly influenced by Mg content, and the alloys with low Mg content are more likely to be in single-Al phase field even if the alloys contain high Cu content. At 748 K (475°C), the dissolution of the second phases is more effective, and the phase components in the thermodynamic equilibrium state are dominated primarily by (Mg + Cu) content, except the alloys with (Mg + Cu) Z 4.35 wt pct, all designed alloys are in single-Al phase field.

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Evolution of eutectic structures in Al-Zn-Mg-Cu alloys during heat treatment

Cited by 100 publications

References 15 publications

Phase Evolution and Mechanical Behavior of the Semi-Solid SIMA Processed 7075 Aluminum Alloy

Phase Evolution and Mechanical Behavior of the Semi-Solid SIMA Processed 7075 Aluminum Alloy

The Role of cobalt and nickel intermetallic phases on the mechanical properties and microstructure evolution of Al-Zn-Mg-Cu alloys

Solidification Paths and Phase Components at High Temperatures of High-Zn Al-Zn-Mg-Cu Alloys with Different Mg and Cu Contents

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