Substantially Pb-Free Aluminum Alloy Composition

Abstract

A substantially Pb-free aluminum alloy consisting essentially of (in weight percent) Si<0.40; Fe<0.70; Cu 5.0-6.0; Zn<0.30; Bi 0.20-0.80; Sn 0.10-0.50 with the remainder being aluminum and incidental impurities. In one embodiment for applications that are sensitive to cracking from stresses generated during machining, the Bi/Sn ratio (in terms of weight percent) is less than 1.32/1 and producing in a T8 temper. On another embodiment for applications that are not sensitive to cracking from stresses during machining but would benefit from smaller machine chip size and more aggressive material removal rates, the aluminum alloy is produced using a T6 temper. The substantially Pb-free aluminum alloy has mechanical properties that include Ultimate Tensile Strength ≥45.0 KSI/311 MPa, Yield Strength ≥38.0 KSI/262 MPa, and % Elongation ≥10%.

1 . A substantially Pb-free aluminum alloy composition comprising the following components (in weight percent of the aluminum alloy composition):
 Pb 0-0.10; Si 0-0.40; Fe 0-0.70; Cu 5.0-6.0; Zn 0-0.30; Bi 0.20-0.80; Sn 0.10-0.50; with the balance being aluminum save for incidental impurities;   said alloy composition having a ratio by weight of Bi/l Sn of less than 1.32/1   said alloy composition manufactured using only a T8 or T6 temper to provide an alloy composition having an Ultimate Tensile Strength ≥45.0 KSI/311 MPa, Yield Strength ≥38.0 KSI/262 MPa, and % Elongation minimum ≥10%.   
     
     
         2 . The composition of  claim 1  wherein said aluminum alloy composition has<0.05 wt. % Pb. 
     
     
         3 . The composition of  claim 1  wherein said aluminum alloy composition comprises 0.10-0.16 wt. % Si. 
     
     
         4 . The composition of  claim 1  wherein said aluminum alloy composition comprises 0.30-0.50 wt. % Fe. 
     
     
         5 . The composition of  claim 1  wherein said aluminum alloy composition comprises 5.1-5.8 wt. % Cu. 
     
     
         6 . The composition of  claim 1  wherein said aluminum alloy composition comprises 0.002-0.05 wt. % Zn. 
     
     
         7 . The composition of  claim 1  wherein said aluminum alloy composition comprises 0.20-0.40 wt. % Bi. 
     
     
         8 . The composition of  claim 1  wherein said aluminum alloy composition comprises 0.20-0.50 wt. % Sn. 
     
     
         9 . The composition of  claim 1  wherein said aluminum alloy compositions comprising, optionally consisting of, the following components (in percent (weight/weight) of the aluminum alloy composition):
 Si 0-0.16; Fe 0-0.50; Cu 5.1-5.8; Zn 0-0.05; Bi 0.20-0.40; and Sn 0.20-0.50. 
 
     
     
         10 . The composition of  claim 1  wherein said aluminum alloy composition has a ratio by weight of Bi/Sn in the range from 1.32/1 to 0.8/1. 
     
     
         11 . The composition of  claim 1  wherein said incidental impurities are present in a total amount of less than 0.5 wt. %. 
     
     
         12 . The composition of  claim 1 , wherein said manufacturing includes only a T8 temper. 
     
     
         13 . The composition of  claim 1 , wherein said aluminum alloy composition is not subjected to a T3 or T4 temper. 
     
     
         14 . A method for forming an aluminum alloy comprising the steps:
 a. casting an alloy billet of the aluminum alloy composition of  claim 1 ,   b. optionally homogenizing the cast billet;   c. extruding the cast billet to form an extrusion having a profile shape;   d. solution heat treating the extrusion by heating to a soak temperature between 900-1060° F. (482-571° C.) and quenching from the soak temperature to room temperature;   e. cold working the extrusion after step d) via drawing, stretching or rolling to a minimum of 5% reduction of cross sectional area; and   f. artificial aging the extrusion of step e) to peak hardness at a T8 or T6 temper to produce said aluminum alloy having an Ultimate Tensile Strength ≥45.0 KSI/311 MPa, Yield Strength ≥38.0 KSI/262 MPa, and % Elongation minimum ≥10%.   
     
     
         15 . The method of  claim 14  wherein
 said step of homogenizing the cast billet occurs at a temperature within the range of 900-1050° F. for a time period of not less than 1 hour; and 
 said step of solution heat treating the extrusion by heating to a temperature between 900-1060° F. (482-571° C.) occurs for 0.5 to 2 hours.