Patent ID: 8613820

Claim:
Method of manufacturing a formed aluminium alloy body-in-white (BIW) part of a motor vehicle, the BIW part having a yield strength of more than 500 MPa after being subjected to a paint-bake cycle, the method comprising: a. providing a rolled aluminium sheet product having a gauge in a range of 0.5 to 4 mm and comprising an aluminum alloy being subjected to a solution heat treatment (SHT) and having been quenched following said SHT, and stored, wherein the whole aluminium alloy sheet after storage and within 10 hours prior to the forming operation is subjected to a further heat treatment wherein it is soaked for a period of 3 seconds to 10 minutes at a temperature in a range of 400° C. to 490° C. and then rapidly cooled or quenched, and wherein the SHT and quenched aluminium alloy of the sheet product has a substantially recrystallised microstructure, and a chemical composition of, in weight percent, Zn 6.9 to 8.0, Mg 1.2 to 2.4, Cu 1.3 to 2.4, Mn<0.3, either 0.05 to 0.25 of Cr or Zr, Si<0.3, Fe<0.35, Ti<0.1, impurities and others each <0.05, total <0.2, balance aluminium, b. forming the aluminium alloy sheet to obtain a formed BIW part, c. assembling the formed BIW part with one or more other metal parts to form an assembly forming a motor vehicle component; d. subjecting said motor vehicle component to a paint bake cycle, wherein the paint bake cycle comprises at least one heat treatment of holding the assembly forming the motor vehicle component at a temperature in a range of 140° C. to 190° C. for a period of 10 to less than 40 minutes, and wherein the aluminium alloy sheet in the formed BIW part has a yield strength of more than 500 MPa.