Edge-on stress-relief of aluminum plates
View Patent ↗In accordance with the present invention, there are provided methods for the manufacture of aluminum alloy plates having reduced levels of residual stress as well as plates and products employing such plates. Processes of the present invention involve providing a solution heat-treated and quenched aluminum alloy plate with a thickness of at least 5 inches, and stress relieving the plate by performing at least one compressing step at a total rate of 0.5 to 5% permanent set along the longest or second longest edge of the plate. In the method, the dimension of the plate where the compression step is performed is along the longest or second longest edge of the plate, which is preferably no less than twice and no more than eight times the thickness of the plate. In further accordance with the present invention, there are provided stress-relieved alloys and plates that are provided with superior W tot properties as well as reduced residual stress and heterogeneity values.
1. A method for stress relieving an aluminum alloy plate having a reduced level of residual stress, said method consisting of
a) providing a solution heat-treated and quenched aluminum alloy plate having an initial thickness at a predetermined location of from about 5 inches to about 40 inches, and having a longest edge and optionally a second longest edge,
b) stress relieving said plate by compressing the plate at a total rate from about 0.5% to about 5% permanent set along said longest or said second longest edge thereof,
wherein the length of the compressed edge of the plate is no less than twice and no more than eight times said initial thickness.
2. A method according to claim 1 , wherein said plate comprises an alloy of the series 2xxx, 6xxx or 7xxx.
3. A method according to claim 1 , wherein said plate has a thickness of less than 40 inches.
4. A method according to claim 1 , wherein said plate has a thickness between 10 and 30 inches.
5. A method according to claim 1 , wherein prior to solution heat-treating and quenching said plate has been subjected to rolling and/or forging.
6. A method according to claim 1 , wherein said compressing is performed in up to three steps with at least partial overlap of compressed areas.
7. A method according to claim 1 , wherein said compressing is performed at a temperature of less than 80° C.
8. A method according to claim 1 , wherein said compressing is performed at a temperature of less than 40° C.
9. A method of claim 1 , wherein said initial thickness is substantially uniform throughout said plate.