| 摘要 |
PROBLEM TO BE SOLVED: To provide an energy absorbing member in an automobile frame structure which has high energy absorptivity, in which cracks are not caused when subjected to compressive deformation in case of a collision. SOLUTION: The member has a composition containing, by weight, 0.5 to 0.75% Si and 0.75 to 1.0% Mg so as to satisfy the relation of -0.05<=(Si-Mg/1.73)<=0.20, and further containing 0.02 to <0.05% Mn and 0.02 to <0.05% Zr, and also containing 0.05 to 0.4% Cu, and further containing 0.1 to 0.4% Fe, 0.005 to 0.1% Ti and 0.0001 to 0.004% B, and the balance Al with inevitable impurities. The member has a crystal grain structure in which the aspect ratio of the crystal grains is <=2. The member has mechanical properties that the ratio of its proof strength to tensile strength is >=0.85, and the proof strength lies in the range of 250 to 290 MPa.
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