Balanced Al-Cu-Mg-Si alloy product

A method of producing a balanced Al—Cu—Mg—Si alloy having a high toughness, good strength levels and an improved fatigue crack growth resistance, comprising the steps of:

• a) casting an ingot consisting of the following composition (in weight percent):
• Cu:
• 4.3-4.9
• Mg:
• 1.5-1.8
• Si:
• 0.10-0.40
• Cr:
• ≦0.15
• 0<Fe≦0.10,
• the balance essentially aluminum and incidental elements and impurities, which are at most 0.05% per element, 0.15% total, wherein the ingot is cast by semi-continuous direct chill (DC) casting,
• b) homogenizing and/or pre-heating the ingot after the casting step,
• c) hot rolling the homogenized and/or pre-heated ingot and optionally cold rolling into a rolled product,
• d) solution heat treating the hot rolled product,
• e) quenching the solution heat treated product,
• f) stretching the quenched product, and
• g) naturally ageing the stretched, rolled and heat-treated product.