Importance

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Abstract

A production method of the present invention includes a step of obtaining an aluminum alloy melt having an alloy composition containing Fe: 0.2 to 0.35 mass %, Cu: 0.05 to 0.20 mass %, Mn: 0.3 to 0.6 mass %, Mg: 1.3 to 2.0 mass %, Zn: 4.6 to 5.1 mass %, and Zr: 0.1 mass % or more, a sum of Zr and Ti being 0.2 mass % or less, the composition satisfying a relation of ([Mg mass %]≧−0.5×[Zn mass %]+3.8) and a relation of ([Ti mass %]/[Zr mass %]≧0.2), and the balance being aluminum and inevitable impurities, and a step of obtaining an aluminum alloy ingot having a structure that has a DAS of 40 μm or less and an average crystal grain diameter of 8 μm or less by continuously casting the aluminum alloy melt at a casting rate satisfying ([maximum casting rate (mm/min)]≦−1.43×[casting diameter (mm)]+500), and a step of obtaining an aluminum alloy cast member by subjecting the aluminum alloy ingot to a homogenization treatment in which the ingot is held for 1 hour at a temperature of 450 to 600° C. By this production method, an aluminum alloy cast member free from anisotropy of plastic deformation is obtained.

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First Claim