| 摘要 |
PROBLEM TO BE SOLVED: To provide an aluminum alloy extruded shape excellent in fatigue strength and most suitably used for an automobile body structure, and its production. SOLUTION: Relating to the aluminum alloy extruded shape for automobile body structure, excellent in fatigue strength, the proportion of the precipitates on a crystalline grain boundary, covering the crystalline grain boundary surface is regulated to <=10%. It is preferable that this extruded shape has a composition which consists of, by weight, 0.3-1.5% Mg, 0.4-2.0% Si, <=2.4% (Mg+Si), <0.8% Cu, and the balance Al with inevitable impurities and to which one or more elements among Zn, Mn, Cr, Zr, V, Fe, and Ti are properly added. In the manufacturing method thereof, a cooling rate after hot extrusion or solution heat treatment is specified to <=1 deg.C/sec or the heat treatment after cooling is specified to >=160 deg.C×1 hr.
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