6000 High-strength 6000-based alloy thick plate having uniform strength in plate thickness direction and method for manufacturing the same

摘要

According to the present invention, a high-strength aluminum alloy thick plate is composed of an aluminum alloy including a prescribed quantity of Si, Mg, Ti, Fe, and a remainder consisting of Al and inevitable impurities. The high-strength aluminum alloy thick plate has a material structure in which an area ratio of Mg_2Si having a circle with an equivalent diameter of 3 m or greater in a plate thickness center portion is 0.45% or less, and an area ratio of Mg_2Si having a circle with an equivalent diameter of 3 m or greater in a region of 201.5 mm from a plate surface in a plate thickness direction is 1.2 times or more and 3.0 times or less the area ratio of Mg_2Si having a circle with an equivalent diameter of 3 m or greater in the plate thickness center portion. The aluminum alloy thick plate has sufficient strength and good uniformity of strength in the plate thickness direction. The aluminum alloy thick plate is able to be manufactured by performing a quenching treatment after cooling the same to cause a difference of a suitable temperature between the plate thickness center portion and a surface after a solution heat treatment.