Annealing Process

Abstract

An annealing process for treatment of an aluminum alloy of AA5XXX series which comprises steps of annealing the aluminum alloy at a first temperature of from about 350° C. to about 450° C. by a rate of temperature increase from about 0.1° C./s to about 0.5° C./s; and cooling down the annealed aluminum alloy to a temperature below 50° C. Aluminum alloys of the AA5XXX series treated by the annealing process of the present invention are also provided.

What is claimed is: 
     
         1 . An annealing process for treatment of an aluminum alloy of AA5XXX series, comprising steps of:
 heating the aluminum alloy to a temperature of from about 350° C. to about 450° C. at a rate of temperature increase from about 0.1° C./s to about 0.5° C./s; and   cooling the heated aluminum alloy to a temperature below about 50° C.   
     
     
         2 . The annealing process of  claim 1 , wherein the aluminum alloy is heated to a temperature is from about 370° C. to about 430° C., or from about 380° C. to about 420° C. 
     
     
         3 . The annealing process of  claim 1 , wherein the aluminum alloy is heated to a temperature is from about 380° C. to about 420° C. 
     
     
         4 . The annealing process of  claim 1 , wherein the rate of temperature increase is from about 0.15° C./s to about 0.45° C./s. 
     
     
         5 . The annealing process of  claim 1 , wherein the rate of temperature increase is from about 0.2° C./s to about 0.4° C./s. 
     
     
         6 . The annealing process of  claim 1 , wherein the rate of temperature increase is from about 0.25° C./s to about 0.35° C./s. 
     
     
         7 . The annealing process of  claim 1 , wherein the cooling step has a cooling rate of from about 10 to about 30° C. per minute, or from about 15° C. to about 25° C. per minute, or from about 18° C. to about 22° C. per minute. 
     
     
         8 . The annealing process of  claim 1 , wherein aluminum alloy has an amount of magnesium in a range of from about 3.0 wt. % to about 10 wt. %, or from about 4.0 wt. % to about 9.5 wt. %, or from about 5.0 wt. % to about 9.0 wt. %, or from about 6.0 wt. % to about 8.5 wt. %. 
     
     
         9 . The annealing process of  claim 1 , wherein aluminum alloy has an amount of element selected from the group consisting of copper, chrome, manganese, zinc, zirconium, beryllium, and scandium. 
     
     
         10 . The annealing process of  claim 1 , further comprising a sensitizing step carried out prior to the heating step, wherein the sensitizing step is performed by heating the aluminum alloy to a temperature of from about 200° C. to about 350° C. 
     
     
         11 . The annealing process of  claim 10 , wherein the sensitizing step comprises:
 heating the aluminum alloy to a temperature of from about 200° C. to about 350° C. at a rate of temperature increase of from about 0.1° C./s to about 0.5° C./s;   maintaining the aluminum alloy at the temperature for a time period of from about 1 minute to about 10 minutes; and   cooling the aluminum alloy to a temperature below about 50° C.   
     
     
         12 . The annealing process of  claim 11 , wherein the temperature of the sensitizing step is from about 250° C. to about 325° C. 
     
     
         13 . The annealing process of  claim 11 , wherein the temperature of the sensitizing step is from about 270° C. to about 310° C. 
     
     
         14 . The annealing process of  claim 11 , wherein the rate of temperature increase in the sensitizing step is from about 0.15° C./s to about 0.45° C./s. 
     
     
         15 . The annealing process of  claim 11 , wherein the rate of temperature increase in the sensitizing step is from about 0.2° C./s to about 0.4° C./s. 
     
     
         16 . The annealing process of  claim 11 , wherein the rate of temperature increase in the sensitizing step is from about 0.25° C./s to about 0.35° C./s. 
     
     
         17 . The annealing process of  claim 11 , wherein the rate of temperature increase in the sensitizing step is from about 0.29° C./s to about 0.32° C./s 
     
     
         18 . The annealing process of  claim 11 , wherein at the end of the sensitizing step, the alloy is maintained at or near the maximum temperature of the sensitizing step for from about 2 minutes to about 8 minutes, or from about 3 minutes to about 7 minutes, or from about 4 minutes to about 6 minutes. 
     
     
         19 . The annealing process of  claim 10 , wherein the sensitizing step, annealing step, and the cooling down step may be repeated for plurality of cycles. 
     
     
         20 . An aluminum alloy of AA5XXX series produced by the annealing process of  claim 1 .