Heat treatable Al alloys excellent in fracture touchness, fatigue characteristic and formability

Abstract

There is provided Al alloys which have improved and excellent fracture toughness and fatigue characteristic and improved formability, and which can be suitably used for transportation machines, such as aircraft, railway vehicles, general mechanical parts and the like. The Al alloy contains 1 to 8% (% by weight, the same is true for the following) of Cu, containing one or more selected from a group comprising 0.4 to 0.8% of Mn, 0.15 to 0.3% of Cr, 0.05 to 0.1% of Zr and 0.1 to 2.5% of Mg, Fe and Si each being less than 0.1%, a distance between constituents being more than 85 .mu.m, and having a micro-structure fulfilling at least one of the following (a) to (c): (a) the size of Al--Mn dispersoids is 4000 .ANG. or more, (b) the size of Al--Cr dispersoids is 1000 .ANG. or more, and (c) the size of Al--Zr dispersoids is 300 .ANG. or more.

Dependencies are inferred from the claim text.