Effect of viscosity on microstructure characteristic in rheological behaviour of wrought aluminium alloys by compression and stirring process

Kim, W. Y.; Kang, Chung Gil; Lee, S. M.

doi:10.1179/174328407x226752

Cited by 10 publications

(7 citation statements)

References 12 publications

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“…the curves correspond to the material's initial resistance due to the previously described three-dimensional skeleton of solid particles. The data showed here are consistent with the results obtained by Kim et al 17,18 : for the AA7075 the author reaches Maximum Stress of 3.5 MPa at 600 °C and Viscosity ranging from 10 4 up to 10 7 Pa.s at Shear rate ranging from 0.03 up to 2 s -1 in a close die compression test. Note, also, that the apparent viscosity decreases markedly in response to longer heat treatment times.…”

Section: Characterization Of the Rheological Behaviorsupporting

confidence: 92%

EValuation of the thixoformability of AA7004 and AA7075 alloys

Zoqui

Torres

2010

Mat. Res.

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This study involved a complete evaluation of the thixoformability of AA7004 and AA7075 alloys, from their microstructural characterization to their viscous behavior. The alloys were subjected to globularization heat treatments for 0, 30, 90 and 210 seconds in two conditions of solid fractions, 45 and 60%, and to viscosity assays under the same conditions. Heat treatments promote the globularization of primary phase particles; hence, the best viscosity results were achieved for alloys with low solid fractions heat-treated for 210 seconds. Alloys AA7004 and AA7075 showed an apparent viscosity of 10 4 to 10 5 (Pa.s). The behavior of materials in this range is similar to that of molten glass and they show high formability. However, the AA7075 alloy showed a better performance than the AA7004 due to the smaller size of its primary particles and original grains, their lower growth during reheating, and depending on the condition, their viscosity of 10 4 Pa.s, which is extremely low for thixoforming standards.

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Section: Characterization Of the Rheological Behaviorsupporting

confidence: 92%

EValuation of the thixoformability of AA7004 and AA7075 alloys

Zoqui

Torres

2010

Mat. Res.

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“…First, 100 g of the DC-cast alloy, SIMA alloy, or slope-cast alloy was placed in a SUS304 crucible coated with Al2O3. Each alloy was heated to and held at 635 °C ± 0.3 °C (fraction of solid fs = 20%) [15] or 630 ± 0.3 °C (fs = 40%) [15] in an electric furnace, as shown in Figure 2a. The measured temperature was inside the error range.…”

Section: Fabrication Of Master Alloysmentioning

confidence: 99%

Effect of Primary Crystals on Pore Morphology during Semi-Solid Foaming of A2024 Alloys

Kubo

Saito

Osaka

et al. 2019

Metals

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We investigated pore formation in aluminum foams by controlling primary crystal morphology using three master alloys. The first one was a direct chill cast A2024 (Al-Cu-Mg) alloy (DC-cast alloy). The others were A2024 alloys prepared to possess fine spherical primary crystals. The second alloy was made by applying compressive strain through a Strain-Induced Melt-Activated process alloy (SIMA alloy). The third one was a slope-cast A2024 alloy (slope-cast alloy). Each alloy was heated to either 635 °C (fraction of solid fs = 20%) or 630 °C (fs = 40%). TiH2 powder was added to the alloys as a foaming agent upon heating them to a semi-solid state and they were stirred while being held in the furnace. Subsequently, A2024 alloy foams were obtained via water-cooling. The primary crystals of the DC-cast alloy were coarse and irregular before foaming. After foaming, the size of the primary crystals remained irregular, but also became spherical. The SIMA and slope-cast alloys possessed fine spherical primary crystals before and after foaming. In addition to average-sized pores (macro-pores), small pores were observed inside the cell walls (micro-pores) of each alloy. The formation of macro-pores did not depend on the formation of the primary crystals. Only in the DC-cast alloy did fine micro-pores exist within the primary crystals. The number of micro-pores in the SIMA and slope-cast alloys was one third of that in the DC-cast alloy.

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“…A2024 alloy foams were fabricated through the melt route at above the liquidus temperature (648 • C [9]) and through the semi-solid route in the range between the liquidus and solidus temperature (510 • C [9]). The effect of the differences in pore morphology and the cell wall structure on compressive properties was then clarified.…”

Section: Discussionmentioning

confidence: 99%

“…In the semi-solid route (Figure 1b), 100 g of the alloy was cut and added to a crucible. The alloy was heated and held at 635 • C (solid fraction f s = 20% [9]) in an electric furnace. The following procedures to obtain the foam were the same as those of the melt route, except that the retaining time was 300 s for the semi-solid route.…”

Section: Sample Preparationmentioning

confidence: 99%

Compressive Properties of A2024 Alloy Foam Fabricated through a Melt Route and a Semi-Solid Route

Kubo

Osaka

Saito

et al. 2019

Metals

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A2024 alloy foams were fabricated by two methods. In the first method, the melt was thickened by Mg, which acts as an alloying element (melt route). In the second method, the melt was thickened by using primary crystals at a semi-solid temperature with a solid fraction of 20% (semi-solid route). A2024 alloy foams fabricated through the semi-solid route had coarse and uneven pores. This led to slightly brittle fracture of the foams, which resulted in larger energy absorption efficiency than that of the foams fabricated through the melt route. Moreover, A2024 alloy foams fabricated through the semi-solid route had a coarser grain size because of the coarse primary crystals. However, by preventing the decrease in the alloying element Mg, the θ/θ’ phase was suppressed. Additionally, by preventing the precipitation of the S′ phase, the amount of Guinier-Preston-Bagaryatsky (GPB) zone increased. This resulted in a larger plateau stress.

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Effect of viscosity on microstructure characteristic in rheological behaviour of wrought aluminium alloys by compression and stirring process

Cited by 10 publications

References 12 publications

EValuation of the thixoformability of AA7004 and AA7075 alloys

EValuation of the thixoformability of AA7004 and AA7075 alloys

Effect of Primary Crystals on Pore Morphology during Semi-Solid Foaming of A2024 Alloys

Compressive Properties of A2024 Alloy Foam Fabricated through a Melt Route and a Semi-Solid Route

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