Edge-on stress-relief of aluminum plates

Abstract

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 manufacturing an aluminum alloy plate having a reduced level of residual stress, said method comprising 
 a) providing a solution heat-treated and quenched aluminum alloy plate having an initial thickness at a predetermined location of at least about 5 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 ) An aluminum alloy wrought plate product having a thickness between about 5 and about 40 inches, wherein said plate has been subjected to a solution heat treatment, and quenching and stress relief by compression at a total rate of 0.5% to 5% permanent set, wherein the stored elastic energy W Tbar  along the T direction is less than 0.5 kJ/m 3 .  
     
     
         10 ) An aluminum alloy wrought product according to  claim 9 , wherein said product has a length L and a width W such that L×W>1 m 2 .  
     
     
         11 ) An aluminum alloy wrought product according to  claim 9 , wherein said product has a length L and a width W such that L×W>2 m 2 .  
     
     
         12 ) An aluminum alloy wrought plate of  claim 9 , wherein the W Tbar  is less than 0.3 kJ/m 3 .  
     
     
         13 ) A method for stress relieving an aluminum alloy plate comprising compressing said plate in a predetermined direction, wherein the efficiency of said stress relief in terms of total stored energy W tot  is 50% or less after said compressing as compared to a standard short transverse stress-relief.  
     
     
         14 ) A method of  claim 1 , wherein said initial thickness is substantially uniform throughout said plate.  
     
     
         15 ) An injection mold comprising a plate according to  claim 9 .  
     
     
         16 ) An injection mold comprising a plate manufactured according to a method of  claim 1 .  
     
     
         17 ) A blow mold comprising a plate according to  claim 9 .  
     
     
         18 ) A blow mold comprising a plate manufactured according to a method of  claim 1 .  
     
     
         19 ) A machined mechanical workpiece comprising a plate manufactured according to a method of  claim 13 .  
     
     
         20 ) A spar suitable for use with an aircraft comprising a plate according to  claim 9.