Abstract: An aluminum alloy member resistant to cracking and having high strengths and excellent stress corrosion cracking resistance is manufactured by expanding a 7xxx aluminum alloy hollow extrusion at a rate of 5% or more. Specifically, a 7xxx aluminum alloy hollow extrusion containing Zn of 3.0-9.5%, Mg of 0.4-2.5%, Cu of 0.05-2.0%, and Ti of 0.005-0.2%, in mass percent, and prepared through press quenching is subjected to a reversion treatment, to pipe expansion within 72 hours after the reversion treatment, and to temper aging. The reversion treatment includes heating at a temperature rise rate of 0.4° C./second or more, holding in a temperature range of 200-550° C. for longer than 0 second, and cooling at a rate of 0.5° C./second or more. The ratio Y (?rs/?0.2) of the tensile residual stress ?rs to the 0.2% yield stress ?0.2 after temper aging and the total content X of Mg and Zn satisfy Expression (1): Y??0.1X+1.

Abstract: An aluminum alloy member resistant to cracking and having high strengths and excellent stress corrosion cracking resistance is manufactured by crushing a 7xxx aluminum alloy extrudate. Specifically, a 7xxx aluminum alloy extrudate containing Zn of 3.0-8.0%, Mg of 0.4-2.5%, Cu of 0.05-2.0%, and Ti of 0.005-0.2%, in mass percent, and prepared through press quenching is subjected to a reversion treatment, to crushing within 72 hours after the reversion treatment, and then to aging. The reversion treatment includes heating at a temperature use rate of 0.4° C./second or more, holding in a temperature range of 200-550° C. for longer than 0 second, and cooling at a rate of 0.5° C./second or more. The ratio of the tensile residual stress ?rs to the 0.2% yield stress ?0.2 after aging and the total content X of Mg and Zn satisfy a condition specified by Expression (1): Y??0.1 X+1.

Abstract: Disclosed is an Al—Mg—Si aluminum alloy extrudate which contains, in terms of mass %, 0.60-1.20% Mg, 0.30-0.95% Si, 0.01-0.40% Fe, 0.30-0.52% Mn, 0.001-0.65% Cu, and 0.001-0.10% Ti and in which the contents of Mg and Si satisfy Mg(%)?(1.73×Si(%)?0.25)?0 and the remainder comprises Al. The extrudate has an equi-axed recrystallized grain texture in which the areal proportion of recrystallized grains is 65% or higher. In examination with a TEM having a magnification of 5,000, intergranular precipitate grains having a size of 1 ?m or more in terms of center-of-gravity diameter are apart from one another at an average spacing exceeding 25 ?m. The average areal proportion of Goss-orientation grains is less than 8% throughout the whole thickness of this extrudate.