PROCEDURE FOR THERMAL TREATMENT OF ITEMS OUT OF HIGH STRENGTH ALUMINIUM ALLOYS Russian patent published in 2016 - IPC C22F1/53 C22C21/10 

FIELD: metallurgy.

SUBSTANCE: procedure for the thermal treatment of items out of high strength aluminium alloys of a system Al - Zn - Mg - Cu, containing in wt %: zinc 6.0-9.0, magnesium 1.6-2.6, copper 0.8-1.6, zirconium 0.07-0.15, iron 0.02-0.15, silicon below 0.1, aluminium and inevitable admixtures - the rest, includes hardening and artificial ageing, contains the stages of isothermal and non-isothermal ageing. First of all, the first stage of isothermal ageing is performed at a temperature of 60-90°C for 10-24 h, then the first stage of non-isothermal ageing is performed by means of the item heating to 160-195°C with the rate of 10-15°C/h, then the second stage of isothermal ageing at a temperature of 160-195°C is performed during the time period determined from the relationship t=ln(473/T)/0.009, where t is the holding time, h, T is the holding temperature, K, and the second stage of non-isothermal ageing is performed by cooling from 160-195°C to 80°C with the rate determined by the equation V=ln(T/88.5)/0.0057, where V is the cooling rate, K/h, T is the holding temperature, K.

EFFECT: reduced sensitivity to laminating, intergranular and pitting corrosion, increased homogeneity of the structure and properties in the item volume, producing the items with improved strength and corrosion characteristics, including for marine conditions operation.

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