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Abstract

An Al--Mg--Si--Cu aluminum alloy plate excelling in strength and formability and exhibiting improved filiform corrosion resistance which is suitably used for automotive body panels. The aluminum alloy plate contains 0.25-0.6% of Mg (mass %, hereinafter the same), 0.9-1.1% of Si, 0.6-1.0% of Cu, and at least one of 0.20% or less of Mn and 0.10% or less of Cr, with the balance consisting of Al and impurities, wherein the number of Q phases (Cu--Mg--Si--Al phases) with a size of 2 .mu.m or more in diameter present in a matrix is 150 per mm.sup.2 or more. The aluminum alloy plate is fabricated by homogenizing an ingot of an aluminum alloy having the above composition at 530.degree. C. or more, cooling the ingot to 450.degree. C. or less at a cooling rate of 30.degree. C./hour or less, hot-rolling the ingot, cold-rolling the hot-rolled product, and providing the cold-rolled product with a solution heat treatment.

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