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 0.2 mm 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 0.1 mm thick specimen than that for the 0.2 mm 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 resistance
* This paper was originally published in Japanese in J. Japan Inst. Metals, 50 (1986), 887.
** School of Engineering, Okayama University, Okayama 700, Japan.
*** Faculty of Engineering, Okayama University of Science, Okayama 700, Japan