THICK AlZnMgCu ALLOY PRODUCTS HAVING IMPROVED PROPERTIES

摘要

A rolled, forged or extruded product made of an AlZnMgCu alloy and having a thickness of more than 60 mm, and a composition as follows (in wt %): 5.9 < Zn < 8.7, 1.7 < Mg < 2.5, 1.4 < Cu < 2.2, Fe < 0.14, Si < 0.11, 0.05 < Zr < 0.15, Mn < 0.02, Cr < 0.02, with Mg + Cu < 4.1, other elements < 0.05 each and < 0.10 in total. The product is treated by dissolving, quenching and optionally annealing, and the T7451 and T7452 treated product has the following properties: (a) a quarter-thickness yield strength R0.2 of over 400 MPa in directions L and TL, (b) a planar deformation resistance greater than 26 MPa 2ROOT m in direction S-L, and greater than 74 - 0.08e - 0.07 R0.2L MPa 2ROOT m in direction L-T (e = thickness in mm), and (c) a stress corrosion threshold higher than 240 MPa. Said products are particularly useful for making structural members for aircraft, and wing spars in particular.