Effects of the Quenching Conditions on the Growth of GP Zones in Al-Zn Alloys

Ohta, Mutsuo; Kanadani, Teruto; Sakakibara, Akira

doi:10.2320/jinstmet1952.47.5_375

Cited by 11 publications

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“…Curves for all specimens with different thickness show initial increase, maximum and decrease, typical of GP zone formation, but the final resistance attained after long aging fairly differs each other; the thinner the specimen the higher the final resistance [8,9]. It has been observed previously that decrease from the maximum resistivity reflects the extent of competitive growth, that is, smaller decrease (higher resistance) corresponds to smaller average size of GP zones [2,10,11]. Thus the result that thinner specimen, where contribution of surface layer is larger, shows higher final resistance means formation of smaller GP zones in the surface layer.…”

Section: Aluminium Alloys 2006 -Icaa10mentioning

confidence: 61%

Effect of an Addition of Silver on the Age Hardening and the Formation of a Soft Surface Layer in an Al-12mass%Zn Alloy

Kanadani

Nakagawa

Hosokawa

et al. 2006

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The aging of Al-Zn alloys has been vastly studied for decades. In the previous paper, 0hta et al. studied carefully the hardness of the alloy during aging and revealed the existence of softer regions near the surface and the grain boundary than the interior of the specimen even after aging for a long time. Electrical resistivity measurement and X-ray small angle scattering experiment together with hardness test suggested that in these regions vacancy decay to the surface and grain boundaries was severe, thus the growth of GP zones were suppressed and therefore age hardening was retarded. Also, it is well-known that an addition of a small amount of Ag raised solvus temperature of GP zones. In this paper, soft surface layer formed in an Al-12mass%Zn alloy is studied by adding small amount of Ag by means of hardness test and resistometry. Addition of Ag more than 0.1% decreases the thickness of soft surface layer as well as accelerates age hardening rate and suppresses the formation of soft region near the grain boundaries. Higher quenching temperature also reduces the thickness of soft surface layer. Together with the behavior of aging curves of the specimen with various thicknesses, the origin of the soft surface layer is confirmed to be the effective role of surface as sinks for vacancies.

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Section: Aluminium Alloys 2006 -Icaa10mentioning

confidence: 61%

Effect of an Addition of Silver on the Age Hardening and the Formation of a Soft Surface Layer in an Al-12mass%Zn Alloy

Kanadani

Nakagawa

Hosokawa

et al. 2006

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“…2 and 3 which show the results of two quenching media, iced water (0 C, ) and methanol (À80 C, ), can be explained as follows: owing to the rapid cooling to 0 C of iced water and the relatively high rate of cooling from 0 C to À80 C of methanol, 21) many of vacancies and vacancy-hydrogen complexes are quenched-in by iced water quenching, whereas much of the hydrogen in the solid solution is frozen-in by the quenching into methanol (À80 C).…”

Section: Behaviors Of Vacancies and Hydrogen And Variationsmentioning

confidence: 99%

Effects of Hydrogen on the Vacancy Formation in Magnesium

2008

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Quenching and annealing experiments with electrical resistivity measurements were applied to magnesium to investigate the formation of thermal vacancies. Two specimens made from materials differing in impurity contents were examined. One of the specimens quenched in a methanol bath at À80C from elevated temperatures ranging from 160 C to 500 C revealed a significant decrease in electrical resistance after annealing for 10 min in the bath. Based on the annealing behaviors at low temperatures (À100 C to À60 C) after the quenching from 200 C, this decrease is thought to be due to the presence of hydrogen in solution. The other specimen, presumably containing smaller amounts of hydrogen, was quenched in iced water from elevated temperatures (200 C-560 C) which yielded results characterized by two thermal activation processes. These processes had the activation energies 54.1 kJ/mol (0.56 eV) and 89.8 kJ/mol (0.93 eV) for the lower and higher quenching temperature ranges, respectively. The former is ascribed to the formation energy of a vacancy interacting with hydrogen and the latter to the intrinsic formation energy of a vacancy. The difference between these energies, 35.7 kJ/mol (0.37 eV), is the binding energy between a vacancy and a hydrogen atom.

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“…The method of heat treatment was the same as described previously (3). It has been reported(4) that dezincification did not occur when Al-Zn alloys were heat-treated in the air.…”

Section: Specimenmentioning

confidence: 99%

Effect of Specimen Thickness on the Aging of Al–Zn Alloys

et al. 1987

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Effect of the specimen thickness on the aging of Al-4 and 10 mass%Zn alloys was studied by measuring the electrical resistance and the intensity of small-angle X-ray scattering (SAXS). When the quenching temperature (TQ) was high, the value of resistance attained at the stage of aging where the change in resistivity ceased virtually was not influenced by the specimen thickness. In the case of low TQ, the resistance was higher for the thin specimen because of the impoverishment of vacancies. The total amount of GP zones formed decreased with decreasing thickness or TQ in the case of low TQ, but did not depend upon the thickness or TQ in the case of high TQ. Both the Guinier radius and the Porod radius for the specimen of 0.1 mm thickness were smaller than those for the 0.2mm thick one when TQ was low, but they became independent of thickness when TQ was high. The quenching temperature at which the Guinier radius was maximum, was higher for the 0.1mm thick specimen than that for the 0.2mm thick one. These results are discussed from the viewpoint of the diffusion of vacancies to the surface and their annihilation during aging. (Received March 16, 1987) Keywords: aging, aluminum-zinc alloy, small-angle X-ray scattering, integrated intensity, Guinier radius, Porod radius, vacancy diffusion, surface, electrical resistanceMany experiments have been conducted on the aging of Al-Zn alloys using various methods and dimensions of specimens. For instance, the thickness of specimens when heat-treated is about 0.1mm for electron microscopy or small-angle X-ray scattering (SAXS), and more than 1mm for hardness testing.The present authors(1) previously used the hardness test to study the age hardening of the Al-12 mass%Zn alloy aged at room temperature. They found that the Vickers hardness number depended on the location of indentation in the grain of the specimen aged after quenching from a low temperature. The hardness number near the grain boundary (within surface was slightly smaller than that of the interior of the grain. Small spherical GP zones were observed, by using an electron microscope, in the thin foil made from the region near the surface of the aged specimen of 1 mm thickness, while there were ellipsoidal, a little larger zones in the foil made from the interior region. These findings have been interpreted as signifying the suppression of the growth of GP zones in the regions near the grain boundaries and the regions near the specimen surface, due to a decrease in the vacancies induced by effective annihilation at the grain surface as well as at the internal sinks, such as dislocations.According to the above interpretation, it may be expected that the process of aging, total amount of GP zones formed, etc. are more or less different between the specimens of less than 0.1mm thickness and those of more than 0.2mm thickness. Thus the thickness of the specimen is considered to be one important factor for understanding the process of aging. In this article, the effect of thickness on the aging of Al-4mass%Zn and Al...

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Effects of the Quenching Conditions on the Growth of GP Zones in Al-Zn Alloys

Cited by 11 publications

References 0 publications

Effect of an Addition of Silver on the Age Hardening and the Formation of a Soft Surface Layer in an Al-12mass%Zn Alloy

Effect of an Addition of Silver on the Age Hardening and the Formation of a Soft Surface Layer in an Al-12mass%Zn Alloy

Effects of Hydrogen on the Vacancy Formation in Magnesium

Effect of Specimen Thickness on the Aging of Al–Zn Alloys

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Effects of the Quenching Conditions on the Growth of GP Zones in Al-Zn Alloys

Cited by 11 publications

References 0 publications

Effect of an Addition of Silver on the Age Hardening and the Formation of a Soft Surface Layer in an Al-12mass%Zn Alloy

Effect of an Addition of Silver on the Age Hardening and the Formation of a Soft Surface Layer in an Al-12mass%Zn Alloy

Effects of Hydrogen on the Vacancy Formation in Magnesium

Effect of Specimen Thickness on the Aging of Al&ndash;Zn Alloys

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Effect of Specimen Thickness on the Aging of Al–Zn Alloys