Microstructure and Mechanical Properties of Cast and Wrought Al-Zn-Mg-Cu Alloys Modified with Zr and Sc

Milman, Yu.V.; Sirko, A.I.; Lotsko, D. V.; Senkov, O.N.; Miracle, Daniel B.

doi:10.4028/www.scientific.net/msf.396-402.1217

Cited by 41 publications

(14 citation statements)

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“…On the other hand, with the addition of Zr and Sc into the Al alloy melt, large quantities of Al 3 (Zr,Sc) particles are generated throughout the melt [17] . As Al 3 (Zr,Sc) particles are excellent heterogeneous nucleants for Al, primary α-Al grains are formed on these effective nucleation sites, leading to much finer slurry microstructure over EMS [18] .…”

Section: Discussionmentioning

confidence: 99%

Semisolid slurry of 7A04 aluminum alloy prepared by electromagnetic stirring and Sc, Zr additions

Zhao

Guo

et al. 2017

China Foundry

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[1][2][3] . Semisolid slurry preparation is one of the most critical steps for semisolid casting, and its primary goal is to prepare slurry with uniformly distributed fine globules. Among various methods [4][5][6][7] of semisolid slurry preparation, electromagnetic stirring (EMS) is particularly attractive as the stirring intensity can be easily controlled and the melt is free of pollution [8][9][10] . However, the slurry primary phase in a large diameter maker (hereafter referred to as large volume slurry) is hard to be refined and homogenized due to the sharp decrease of electromagnetic force from the Abstract: Slurry preparation is one of the most critical steps for semisolid casting, and its primary goal is to prepare slurry with uniformly distributed fine globules. In this work, electromagnetic stirring (EMS) and the addition of Sc and Zr elements were used to prepare semisolid slurry of 7A04 aluminum alloy in a large diameter slurry maker. The effects of different treatments on the microstructure, composition and their radial homogeneity were investigated. The results show that, compared to the slurry without any treatment, large volume slurry with finer and more uniform microstructure can be obtained when treated by EMS, Sc, or Zr additions individually. EMS is more competent in the microstructural and chemical homogenization of the slurry while Sc and Zr additions are more excellent in its microstructural refinement. The combined treatment of EMS, Sc and Zr produces premium 7A04 aluminum alloy slurry with uniformly distributed fine α-Al globules and composition. The interaction mechanism between EMS and Sc and Zr additions was also discussed. periphery to the interior [11,12] . Scandium (Sc) and zirconium (Zr) are potent grain refiners for Al alloys [13,14] . With the addition of Sc and Zr elements (hereafter referred to as GR), numerous heterogeneous nuclei can be formed in Al alloy slurry, which also can contribute to the refinement and homogeneity of the slurry microstructure. For these reasons, the compound treatment including EMS, Sc and Zr additions is supposed to obtain large volume slurry with well dispersed fine primary α-Al globules. In this research, the effect of combined treatment of EMS, and Sc and Zr additions on the microstructure and the homogenizing of aluminum alloy large volume slurry was investigated.

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Section: Discussionmentioning

confidence: 99%

Semisolid slurry of 7A04 aluminum alloy prepared by electromagnetic stirring and Sc, Zr additions

Zhao

Guo

et al. 2017

China Foundry

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“…The synergistic grain refining effect from Sc and Zr added together has been reported in a number of publications (see, for example [4][5][6][7][8][9][10][11] ) and it has been explained by the presence of primary Al 3 (Sc,Zr) particles, which solidify first and contribute to crystallization in these alloys.…”

Section: Microstructurementioning

confidence: 99%

“…[1,2] The strengths of these alloys generally increase with the concentrations of Zn and Mg; however the alloys become prone to hot cracking during casting or during rapid cooling from a processing temperature when the amount of Zn exceeds 7-8%. Fortunately, the fracturerelated properties of these alloys can considerably be improved by small additions of Sc [3][4][5] , which enables superior combination of higher strength levels and acceptable ductility [6][7][8] .…”

Section: Introductionmentioning

confidence: 99%

Microstructure and properties of cast ingots of Al-Zn-Mg-Cu alloys modified with Sc and Zr

Senkov

Bhat

Senkova

et al. 2005

Metall Mater Trans A

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The effect of combined additions of Sc and Zr on the microstructure and tensile properties of the direct chill (DC) cast ingots of developmental Al-Zn-Mg-Cu alloys has been evaluated in this work. The properties in both the longitudinal and transverse directions of the cast ingots were determined in as-cast and cast plus heat-treated conditions, at room and cryogenic temperatures.Extensive microstructural evaluation was carried out using optical and electron microscopy, including orientation image microscopy by the electron backscatter diffraction technique. The Sc-containing developmental cast alloys showed the tensile properties, which are much better than the properties of any commercial cast Al alloys and are similar or even superior to the properties of 7075-T6 alloy forgings. The microstructural evolution, the strengthening mechanisms, optimum content of the dispersoid-forming elements, and the processing-structureproperty correlations are discussed.

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“…[24] There are reports that the Sc addition to these alloys slows, [28] accelerates, [19,21] or does not affect [29] the precipitation of g¢ particles. During solution treatment prior to aging, coarsening of the Al 3 Sc particles should occur, which also may affect the final properties.…”

mentioning

confidence: 99%

“…Proper thermomechanical treatment, which may involve hot working, such as forging, hot rolling, or extrusion, significantly improves the mechanical properties. [2] Fortunately, the fracture-related properties of these alloys can be considerably improved by small additions of Sc and Zr, [18,19] which enable a superior combination of higher strength levels and acceptable ductility, both in wrought [20,21] and cast [22,23] conditions. The beneficial effects from additions of Sc and Zr to different aluminum alloys are discussed in a recent review.…”

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confidence: 99%

Effect of Sc on Aging Kinetics in a Direct Chill Cast Al-Zn-Mg-Cu Alloy

Senkov

Senkova

Шагиев

2008

Metall Mater Trans A

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The effect of Sc additions on precipitation strengthening in a direct chill (DC) cast Al-Zn-Mg-Cu alloy was studied after natural and artificial aging. The microhardness, room temperature (RT) mechanical properties, and phase composition of the alloys were determined after different steps of aging. The strengthening mechanisms were discussed. It was shown that minor additions of Sc increased the strength of the Al-Zn-Mg-Cu alloy after casting and solution heat treatment, due to the precipitation of fine coherent Al 3 (Sc,Zr) particles. An analysis of the aging kinetics revealed that Sc had no effect on the natural aging, which was controlled by the formation and growth of Guinier-Preston (GP) I zones. On the other hand, the Sc additions accelerated the aging process at 120°C and 150°C within a period of time of the formation and growth of GP II zones and g¢ particles. It was concluded that the presence of Sc accelerated the formation and growth of GP II zones in the Al-Zn-Mg-Cu alloys, which led to the earlier precipitation of the g¢ phase. However, at longer aging times at 120°C and 150°C, the aging response of the Sc-containing alloys slowed down, due to faster coarsening of the g¢ particles and their transformation into g particles. A model of the formation of vacancy-rich clusters (VRCs), precursors to GP zones, in the Al-Zn-Mg-based alloys was proposed. According to this model, the observed effects of Sc on aging are the result of the Sc-induced increase in the number density of the GP II clusters and the concentration of quenched-in solute-bound excess vacancies.

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Microstructure and Mechanical Properties of Cast and Wrought Al-Zn-Mg-Cu Alloys Modified with Zr and Sc

Cited by 41 publications

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Semisolid slurry of 7A04 aluminum alloy prepared by electromagnetic stirring and Sc, Zr additions

Semisolid slurry of 7A04 aluminum alloy prepared by electromagnetic stirring and Sc, Zr additions

Microstructure and properties of cast ingots of Al-Zn-Mg-Cu alloys modified with Sc and Zr

Effect of Sc on Aging Kinetics in a Direct Chill Cast Al-Zn-Mg-Cu Alloy

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