Nkk Corporation

Tetsuo Sakiyama

Kuninori Minakawa

Seishi Tsuyama

A heat treating method for a high strength aluminum alloy comprising the steps of: solution heat treating of an aluminum alloy consisting essentially of about 3 to 9 wt. % Zn, 1 to 6 wt. % Mg, 1 to 3 wt. % Cu, at least one element selected from the group consisting of 0.1 to 0.5 wt. % Cr, 0.1 to 0.5 wt. % Zr, 0.2 to 1.0 wt. % Mn, and the balance being Al, heating of the solution heat treated alloy to a temperature of a lower temperature zone of from 100.degree. to 140.degree. C. and optionally maintaining the alloy at a temperature within the lower temperature zone for a duration of time, reheating of the alloy to a temperature of an upper temperature zone of from 160.degree. to 200.degree. C. and optionally maintaining the alloy at a temperature within the upper temperature zone for a second duration of time, cooling of the alloy to a temperature of the lower temperature zone, and repeating the steps (2), (3), and (4) at least twice.

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Kawasaki, Japan

Tetsuo Sakiyama