DIRECT CHILL CAST ALUMINUM INGOT WITH COMPOSITION GRADIENT FOR REDUCED CRACKING
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)