7xxx series aluminum alloy member excellent in stress corrosion cracking resistance and method for manufacturing the same

A method for manufacturing a 7xxx series aluminum alloy member, the method comprising the steps of:

• subjecting a 7xxx series aluminum alloy hollow extrusion to a reversion treatment;
• subjecting the hollow extrusion to pipe expanding at an expansion rate of 5% or more within 72 hours after the reversion treatment to give a member;
• and
• temper aging the member after the pipe expanding;
• wherein:
• the 7xxx series aluminum alloy hollow extrusion comprises:
• Zn in a content of from 3.0 to 9.5 percent by mass;
• Mg in a content of from 0.4 to 2.5 percent by mass;
• Cu in a content of from 0.05 to 2.0 percent by mass;
• and
• Ti in a content of from 0.005 to 0.2 percent by mass;
• the hollow extrusion further comprises Al and inevitable impurities;
• the hollow extrusion is manufactured through press quenching;
• and
• the step of reversion treatment comprises the substeps of:
• heating the material at a rate of temperature rise of 0.4° C./second or more;
• holding the material in a temperature range of from 200° C. to 550° C. for a duration of longer than 0 second;
• and
• subsequently cooling the material at a cooling rate of 0.5° C./second or more.