Aluminium alloy and extrusion

Abstract

A population of extrusion billets has a specification such that every billet is of an alloy of composition (in wt. %): Fe <0.35; Si 0.20-0.6; Mn <0.10; Mg 0.25-0.9; Cu <0.015; Ti <0.10; Cr <0.10; Zn <0.03; balance Al of commercial purity. After ageing to T5 or T6 temper, extruded sections can be etched and anodized to give extruded matt anodized sections having improved properties.

1 . A population of billets resulting from more than one cast of metal having a specification such that every billet has a composition (in wt %):  
       
         
           
                 
                 
                 
               
                     
                 
                     
                 
                   Constituent 
                   Range 
                   Preferred 
                 
                     
                 
                   Fe 
                   <0.35 
                   0.16-0.35 
                 
                   Si 
                   0.20-0.6 
                   0.4-0.6 
                 
                   Mn 
                   <0.10  
                   0.01-0.05 
                 
                   Mg 
                   0.25-0.9 
                   0.35-0.6  
                 
                   Cu 
                   <0.015 
                   <0.010 
                 
                   Ti 
                   <0.10  
                   <0.05  
                 
                   Cr 
                   <0.10  
                   <0.09  
                 
                   Zn 
                   <0.03  
                   <0.03  
                 
                     
                 
                   
                    
                   
                 
                     
                 
             
                
                
                
                
               
               
                
                
                
                
                
                
                
                
                
                
                
               
            
           
         
       
     
     
         2 . A billet taken from the population of billets of  claim 1 .  
     
     
         3 . A method of making an extruded section by extruding the billet according to  claim 2 .  
     
     
         4 . A method as claimed in  claim 3 , wherein the extruded section is aged by heating at 1500-200° C. for a time to develop peak strength.  
     
     
         5 . A method as claimed in  claim 3  or  claim 4 , wherein the extruded section is etched and anodised.  
     
     
         6 . An extruded section made by the method of any one of  claims 3  to  5 .  
     
     
         7 . A method of making a population of billets by performing more than one cast of metal having a specification such that every billet has the composition set out in claim  1 .