Isothermal precipitation of commercial 3003 Al alloys studied by thermoelectric power

Luiggi, Ney

doi:10.1007/s11663-997-0135-y

Cited by 19 publications

(4 citation statements)

References 20 publications

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“…Enhanced surface deformation is reported to have effect on solid solubility and precipitation kinetics. 16,17 Previous work [18][19][20][21][22][23] on the effect of plastic deformation on the precipitation kinetics of the manganese-bearing phases ␣-(Fe, Mn) 3 SiAl 12 and (Mn, Fe͒Al 6 indicate that deformation reduces the temperatures at which precipitation starts, and may increase the rate of precipitation at a given temperature by orders of magnitude. Hence, for similar heattreatments, greater precipitation occurs at the surface layer than in the bulk material.…”

Section: Discussionmentioning

confidence: 99%

Electrochemical Behavior of the Active Surface Layer on Rolled Aluminum Alloy Sheet

Ambat

Davenport

Afseth³

et al. 2004

J. Electrochem. Soc.

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The highly deformed, micrograined layer on the outermost surface of a rolled Al-Fe-Si-Mn model alloy was electrochemically characterized. The thickness of this deformed surface layer in a 1.0 mm thick sheet was approximately 1 m. Polarization curves in 5% NaCl solution at pH 3.0 and 11.5 were obtained at different depths from the surface using controlled sputtering in a glow discharge optical emission spectrometer for sample preparation. Both the anodic and the cathodic reactivity of the deformed surface layer were significantly higher than that of the bulk. Consistent with this, image analysis of scanning electron microscopy backscattered images revealed an increased number of fine intermetallic particles in the surface layer as compared with the bulk of the material. The corrosion morphology of the outermost surface was characterized by a high density of fine pits, while fewer and larger pits were observed in the bulk. The results highlight the importance of heavily deformed surface layers in controlling corrosion behavior of rolled aluminum products.During the production of aluminum sheet, the surface of the material receives different thermomechanical treatment from the bulk. As a result of friction between the sheet surface and the work rolls during rolling, the outermost layer of aluminum metal is subjected to significantly higher levels of strain than the underlying bulk material. This enhanced shear deformation of the surface results in a very different microstructure compared with the bulk. 1-3 The surface layer is characterized by a very fine, submicrometer grain size and contains incorporated second phase particles, primarily oxides, which prevent recrystallization. During subsequent heattreatment, precipitation of fine intermetallic phases can occur preferentially in the surface layer, resulting in a higher dispersoid density and lower solute levels than bulk. 4,5 Fine intermetallic phases are also formed at the surface by fragmentation of the particles already present at the surface.Afseth et al. 6-10 have found a strong correlation between the presence of deformed layers and filiform corrosion susceptibility of 3xxx and 5xxx series aluminum alloys. The hot-rolled material is more susceptible to filiform attack than the cold-rolled material, and the susceptibility increases further with heat-treatment. 8 The microstructure of the materials reveals the presence of fine intermetallic phases within the thin deformed layer, although the investigation could not establish significant change in solid solution Mn content at the surface. 9 Removal of the active surface layer by caustic etching improved the filiform susceptibility of the material. 8 Etching also removed the substrate sensitivity to heat-treatment, indicating that the enhanced precipitation is associated with the deformed layer. By cold-rolling a corrosion-resistant etched sample, the sensitivity to filiform attack after heat-treatment can be reintroduced. 8 The effect is associated with the precipitation of intemetallic particles during thermo...

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Section: Discussionmentioning

confidence: 99%

Electrochemical Behavior of the Active Surface Layer on Rolled Aluminum Alloy Sheet

Ambat

Davenport

Afseth³

et al. 2004

J. Electrochem. Soc.

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“…Enhanced deformation of aluminium alloys has an effect on precipitation kinetics. Luiggi (21,22) studied the effect of plastic deformation on the precipitation kinetic of AA 3003, which contains Al 6 (MnFe) and α-Al 12 (MnFe) 3 Si intermetallic particles, using the thermoelectric power (TEP) technique. It was found that Mn diffusion is the dominant process in the precipitation kinetics.…”

Section: Resultsmentioning

confidence: 99%

Effect of Equal Channel Angular Extrusion on Corrosion Behavior of Al-Mn ALLOY

Namahoot¹,

Davenport²,

Ambat³

et al. 2008

ECS Trans.

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Effect of deformation on the corrosion behaviour of Al-1Mn-0.4Fe-0.3Si model alloy was studied after equal channel angular extrusion (ECAE) to different levels and subsequent annealing treatment. During polarisation, cathodic reactivity of the samples increases with the degree of ECAE deformation. Microstructure showed more number of intermetallic particles after ECAE deformation as well as after annealing. ECAE deformation also increased the anodic reactivity. Observed electrochemical behaviour is attributed to intermetallic particles as they good cathodic sites and precipitation of particles deplete manganese from matrix leading to higher anodic activity.

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“…The thermoelectric power variation from one temperature to another induces changes in atomic concentration that blend with the structural transformation in such a way that the derivative of the thermoelectric power, as in other techniques, will show peaks and troughs characteristic of the different reactions; that is, the derivative of the thermoelectric power allows for direct observation of the kinetics of phase changes occurring during a specific thermal treatment. It is important for our analysis to indicate that the specific Δ values [17] for Fe and Si are −8.00 and −0.74 V/K and that the specific Δ values are 2.56 and 1.02 Ω cm/wt%, respectively. With these values, theoretical equations (3) and (4), the particular microstructural conditions, and the contributions of Fe and Si to the TEP can be evaluated.…”

Section: Thermoelectric Powermentioning

confidence: 97%

Experimental Study of the Interaction between Recrystallization and Precipitation Processes of an AA8011 Commercial Alloy

Luiggi

Valera

Rodriguez

et al. 2014

Journal of Metallurgy

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Phase changes in a commercial AA8011 alloy from different initial microstructure conditions were studied using thermoelectric power (Δ ), differential scanning calorimetry (DSC), and transmission electron microscopy (TEM) techniques with the purpose of obtaining evidence of the interaction between recovery-precipitation and recrystallization-precipitation processes occurring during nonisothermal heating at different rates. Thermoelectric power and its thermal derivative reflect this evidence by a displacement of the characteristic precipitation peaks, the recovery and recrystallization contributions remaining masked by the strong incidence of the iron precipitation on that property, while DSC measurements detect the emergence of new peaks not observed on thermograms of homogenized samples. An exhaustive study of these peaks permits direct differentiation between precipitation and recoveryrecrystallization contributions. TEM confirms the interaction between both processes by means of local observations.

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Isothermal precipitation of commercial 3003 Al alloys studied by thermoelectric power

Cited by 19 publications

References 20 publications

Electrochemical Behavior of the Active Surface Layer on Rolled Aluminum Alloy Sheet

Electrochemical Behavior of the Active Surface Layer on Rolled Aluminum Alloy Sheet

Effect of Equal Channel Angular Extrusion on Corrosion Behavior of Al-Mn ALLOY

Experimental Study of the Interaction between Recrystallization and Precipitation Processes of an AA8011 Commercial Alloy

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