| 摘要 |
PROBLEM TO BE SOLVED: To efficiently increase the strength of an Al alloy extruded material in a short time and to reduce the energy cost by executing artificial age harden ing treatment for an Al-Mg-Si base Al alloy extruded material by two stage treatment in which the temps. are specified. SOLUTION: At the time of subjecting an extruded material obtd. by subjecting an Al-Mg-Si base Al alloy to extrusion and thereafter executing rapid cooling and modifying to artificial age hardening treatment, the treatment is executed dividedly into two stages. At first, primary preaging treatment is executed in the temp. range of 160 to 180 deg.C to uniformly precipitate Mg2 Si precipitating phases. Next, secondary aging treatment is executed in the temp. range of 195 to 220 deg.C for 1.5 to 8.0 hr to grow Mg2 Si precipitating phases precipitated at the time of the primary preaging treatment. It is preferable that the holding time in the primary treatment is regulated to 0.5 to 1.5 hr and the holding time in the secondary treatment is regulated to 1.5 to 3.0 hr. Furthermore, it is preferable thatΔT, i.e., the difference between the primary preaging treatment time and the secondary aging treatment time satisfiesΔT>=25 deg.C.
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