Direct chill cast aluminum ingot with composition gradient for reduced cracking

Abstract

Described are methods of preparing compositionally gradient aluminum alloy products. The methods may include casting a composite ingot in a mold. The composite ingot may include an inner region comprising a first aluminum alloy, an outer region surrounding the inner region, and a compositionally gradient zone between the inner region and the outer region. The outer region may include a second aluminum alloy different from the first aluminum alloy. At least one alloying element of the first aluminum alloy may have a content that is decreased through the compositionally gradient zone in a direction from the inner region to the outer region. Also described are aluminum alloy composite ingots and rolled aluminum alloy products having a compositionally gradient zone.

1 . A method of preparing a compositionally gradient aluminum alloy product, comprising:
 casting a composite ingot in a mold, the composite ingot including:
 an inner region comprising a first aluminum alloy, 
 an outer region surrounding the inner region, the outer region comprising a second aluminum alloy different from the first aluminum alloy; and 
 a compositionally gradient zone between the inner region and the outer region, wherein at least one alloying element of the first aluminum alloy has a content that is decreased through the compositionally gradient zone in a direction from the inner region to the outer region. 
   
     
     
         2 . The method of  claim 1 , wherein the first aluminum alloy and the second aluminum alloy are cast concurrently. 
     
     
         3 . The method of  claim 1 , further comprising scalping the composite ingot to remove, from a rolling surface, at least a portion of the compositionally gradient zone and the outer region. 
     
     
         4 . The method of  claim 3 , wherein scalping includes removing material to generate a monolithic ingot comprising the first aluminum alloy. 
     
     
         5 . The method of  claim 1 , wherein the first aluminum alloy comprises a 7xxx series aluminum alloy, a 5xxx series aluminum alloy, or a 2xxx series aluminum alloy. 
     
     
         6 . (canceled) 
     
     
         7 . The method of  claim 1 , wherein the second aluminum alloy comprises a lxxx series aluminum alloy. 
     
     
         8 . The method of  claim 7 , wherein the second aluminum alloy has a purity of at least 99.7%. 
     
     
         9 . The method of  claim 1 , wherein the at least one alloying element of the first aluminum alloy comprises Zn, Cu, Mg, or Na. 
     
     
         10 . The method of  claim 1 , wherein the outer region is substantially devoid of the at least one alloying element. 
     
     
         11 . The method of  claim 1 , wherein the composite ingot is substantially devoid of cracking. 
     
     
         12 . (canceled) 
     
     
         13 . The method of  claim 1 , wherein the composite ingot is substantially devoid of porosity. 
     
     
         14 . (canceled) 
     
     
         15 . The method of  claim 1 , wherein casting the composite ingot comprises a direct chill casting process in which the inner region and the outer region are co-cast in an arrangement where the outer region is contacted with cooling water. 
     
     
         16 . The method of  claim 1 , wherein the outer region has a thickness of from 7% to 15% of a total thickness of the composite ingot. 
     
     
         17 . The method of  claim 16 , wherein the compositionally gradient zone has a thickness of from 2% to 10% of a total thickness of the composite ingot. 
     
     
         18 . (canceled) 
     
     
         19 . The method of  claim 1 , further comprising one or more of a homogenization process, a hot rolling process, a cold rolling process, an annealing process, a solution heat treatment process, a quenching process, or a surface treatment process. 
     
     
         20 . The method of  claim 1 , further comprising directing a magnetic field during casting, the magnetic field configured to suppress turbulence in a direction perpendicular to the compositionally gradient zone. 
     
     
         21 . The method of  claim 1 , wherein the first aluminum alloy is delivered to the mold from a first height and the second aluminum alloy is delivered to the mold from a second height, wherein the second height is different from the first height. 
     
     
         22 . The method of  claim 21 , further comprising directing a magnetic field during casting to suppress turbulence in a direction perpendicular to the compositionally gradient zone, wherein directing the magnetic field includes (1) positioning the magnetic field at a height between the first height and the second height and/or (2) providing a skim dam, the skim dam being positioned within molten liquid at a height between the first height and the second height. 
     
     
         23 . (canceled) 
     
     
         24 . (canceled) 
     
     
         25 . An aluminum alloy composite ingot, comprising:
 an inner region comprising a first aluminum alloy,   an outer region surrounding the inner region, the outer region comprising a second aluminum alloy different from the first aluminum alloy; and   a compositionally gradient zone between the inner region and the outer region, wherein at least one alloying element of the first aluminum alloy has a content that is decreased through the compositionally gradient zone in a direction from the inner region to the outer region.   
     
     
         26 - 38 . (canceled) 
     
     
         39 . A rolled aluminum alloy product, comprising:
 an inner region comprising a first aluminum alloy,   an outer region surrounding the inner region, the outer region comprising a second aluminum alloy different from the first aluminum alloy; and   a compositionally gradient zone between the inner region and the outer region, wherein at least one alloying element of the first aluminum alloy has a content that is decreased through the compositionally gradient zone in a direction from the inner region to the outer region.   
     
     
         40 - 52 . (canceled)