7xxx wrought products with improved compromise of tensile and toughness properties and method for producing

A process for manufacture of a wrought 7xxx aluminum-based alloy products, comprising:

• a) preparing a bath of molten alloy metal comprising in weight-% (wt. %)
• Zn
• 6.65
• -
• 7.45
• Mg
• 1.35
• -
• 1.75
• Cu
• 1.85
• -
• 2.35
• Zr
• 0.04
• -
• 0.14
• Mn
• ⁢
• ⁢
• 0
• -
• 0.5
• Ti
• ⁢
• 0
• -
• 0.15
• ,
• optionally
• ⁢
• from
• 0.02
• to
• 0.06
• wt
• .
• %
• ,
• V
• ⁢
• 0
• -
• 0.15
• Cr
• ⁢
• 0
• -
• 0.25
• Fe
• ≤
• 0.05
• Si
• ≤
• 0.05
• Fe
• +
• Si
• ≤
• 0.08
• ,
• Other impurities <0.05 each and <0.15 total, remainder aluminum,
• b) casting said molten alloy metal to obtain a slab or a billet
• c) homogenizing said ingot or billet to obtain a homogenized ingot or billet,
• d) hot working said homogenized slab or billet to obtain a wrought product, optionally an extruded, rolled and/or forged product, with a final thickness of at least 25 mm;
• e) solution heat treating and quenching said wrought product to obtain a quenched wrought product;
• f) stress relieving the quenched wrought product to obtain a stress relieved wrought product;
• g) artificial aging said stress relieved wrought product wherein total equivalent aging time t(eq) at 155° C. is comprised from 24 hours to 45 hours,
• the total equivalent time t(eq) at 155° C. being defined by the formula:
• t
• ⁡
• (
• eq
• )
• =
• ∫
• exp
• ⁡
• (
• -
• 16000
• /
• T
• )
• ⁢
• dt
• exp
• ⁡
• (
• -
• 16000
• /
• T
• ref
• )
• where T is instantaneous temperature in Kelvin during aging and Tref is a reference temperature selected at 155° C. (428 K), t(eq) is expressed in hours.