Selective Grain Boundary Engineering

Abstract

A process for grain boundary engineering of an aluminum alloy of AA5XXX series which includes steps of annealing the aluminum alloy at a first temperature of from about 350° C. to about 450° C.; deforming the annealed aluminum alloy to reduce the thickness by from about 2% to about 20% of the original thickness of the aluminum alloy; heat treating the deformed aluminum alloy at a second temperature from about 450° C. to about 550° C., and optionally sensitizing the heat treated alloy in one or more sensitizing steps. Aluminum alloys of the AA5XXX series treated by the process of the present invention are also provided.

What is claimed is: 
     
         1 . A process for grain boundary engineering of an aluminum alloy of AA5XXX series, said process comprising steps of:
 annealing said aluminum alloy at a temperature of from about 350° C. to about 450° C.;   deforming said annealed aluminum alloy to reduce the thickness by from about 2% to about 20% of the original thickness of the aluminum alloy; and   heat treating said deformed aluminum alloy at a temperature of from about 450° C. to about 550° C.   
     
     
         2 . The process of  claim 1 , wherein said temperature in said annealing step is from about 370° C. to about 430° C., or from about 380° C. to about 420° C. 
     
     
         3 . The process of  claim 1 , wherein said annealing step is performed for a period from about 0.5 to about 3 hours, or from about 1 to about 2 hours. 
     
     
         4 . The process of  claim 1 , further comprising the step of cooling the annealed aluminum alloy before the deforming step. 
     
     
         5 . The process of  claim 4 , wherein said cooling step has a cooling rate of from about 10 to about 30° C. per minute, or from about 15 to about 25° C. per minute, or from about 18 to about 22° C. per minute. 
     
     
         6 . The process of  claim 1 , wherein said deforming step comprises cold rolling. 
     
     
         7 . The process of  claim 6 , wherein said cold rolling reduces the thickness from 3% to 15%. 
     
     
         8 . The process of  claim 6 , wherein said cold rolling reduces the thickness from 5% to 10%. 
     
     
         9 . The process of  claim 6 , wherein said cold rolling is performed at room temperature. 
     
     
         10 . The process of  claim 1 , wherein said temperature in said heat treating step is from 475° C. to 525° C. 
     
     
         11 . The process of  claim 1 , wherein said temperature in said heat treating step is from 485° C. to 515° C. 
     
     
         12 . The process of  claim 1 , wherein said heat treating step is performed for a period of from about 1 to about 6 hours, or from about 2 to about 5 hours, or from about 2 to about 4 hours. 
     
     
         13 . The process of  claim 1 , further comprising the step of sensitizing said heat treated aluminum alloy. 
     
     
         14 . The process of  claim 13 , wherein said sensitizing step is performed at a temperature of from about 100° C. to about 200° C., or from about 120° C. to about 180° C., or from about 140° C. to about 160° C. 
     
     
         15 . The process of  claim 13 , wherein said sensitizing step is performed for a period of from about 70 to about 150 hours, or from about 80 to about 130 hours, or from about 90 to about 120 hours. 
     
     
         16 . The process of  claim 13 , wherein said sensitizing step comprising a plurality of sensitizing steps. 
     
     
         17 . The process of  claim 16 , wherein each of said plurality of sensitizing steps is performed at a different temperature. 
     
     
         18 . The process of  claim 16 , wherein each of said plurality of sensitizing steps is performed with a low temperature sensitizing step followed by sensitizing steps at higher temperatures. 
     
     
         19 . The process of  claim 16 , wherein each of said plurality of sensitizing steps is performed using a cooling step following each sensitizing step. 
     
     
         20 . An aluminum alloy of AA5XXX series treated by the process of  claim 1 .