Aluminum alloy

Abstract

The aluminum alloy is an aluminum-magnesium-scandium-zirconium alloy having a long term corrosion resistance combined with high strength as compared to standard AA 5052 alloy, and is suitable for use in marine and salt water environments with a minimum of corrosion. The aluminum alloy contains about 2.2-3.0 wt. % magnesium, about 0.1-0.97 wt. % scandium, and about 0.14-0.9 wt. % zirconium. The alloy may also contain about 0.1-0.4% wt. % iron, 0.001-0.2 wt. % chromium, 0.02-0.94 wt. % titanium, and silicon, copper, zinc and manganese up to about 0.20 wt. %, 0.1 wt. %, 0.1 wt. %, and 0.01 wt. %, respectively, either as additives intentionally added during processing or as impurities, the remainder being aluminum.

1 . An aluminum alloy, comprising:
 from about 2.2 to about 3.0 weight percent magnesium;   from about 0.1 to about 0.97 weight percent scandium;   from about 0.14 to about 0.9 weight percent zirconium;   up to about 0.20 weight percent silicon;   up to about 0.1 weight percent copper;   up to about 0.1 weight percent zinc; and   up to about 0.01 weight percent manganese, the balance being aluminum.   
   
   
       2 . The aluminum alloy according to  claim 1 , further comprising from about 0.1 to about 0.4% weight percent iron. 
   
   
       3 . The aluminum alloy according to  claim 1 , further comprising from about 0.001 to about 0.2 weight percent chromium. 
   
   
       4 . The aluminum alloy according to  claim 1 , further comprising from about 0.02 to about 0.94 weight percent titanium. 
   
   
       5 . The aluminum alloy according to  claim 1 , wherein about 0.14 weight percent zirconium is present in the alloy. 
   
   
       6 . The aluminum alloy according to  claim 5 , wherein about 0.15 weight percent scandium is present in the alloy. 
   
   
       7 . The aluminum alloy according to  claim 5 , wherein about 0.3 weight percent scandium is present in the alloy. 
   
   
       8 . The aluminum alloy according to  claim 5 , wherein about 0.6 weight percent scandium is present in the alloy. 
   
   
       9 . The aluminum alloy according to  claim 5 , wherein about 0.9 weight percent scandium is present in the alloy. 
   
   
       10 . The aluminum alloy according to  claim 5 , wherein from about 2.85 to about 3 weight percent magnesium is present in the alloy. 
   
   
       11 . The aluminum alloy according to  claim 1 , wherein the scandium is homogenously distributed throughout the alloy in dispersoids having a diameter of between 15 and 100 nm. 
   
   
       12 . The aluminum alloy according to  claim 1 , wherein the scandium is homogenously distributed throughout the alloy in dispersoids having a diameter of about 15 nm. 
   
   
       13 . An extruded aluminum product formed from the alloy according to  claim 1 . 
   
   
       14 . A cast aluminum billet formed from the alloy according to  claim 1 . 
   
   
       15 . An aluminum alloy, consisting essentially of:
 from about 2.2 to about 3.0 weight percent magnesium;   from about 0.1 to about 0.97 weight percent scandium;   from about 0.14 to about 0.9 weight percent zirconium;   up to about 0.20 weight percent silicon;   up to about 0.1 weight percent copper;   up to about 0.1 weight percent zinc; and   up to about 0.01 weight percent manganese, the balance being aluminum.   
   
   
       16 . The aluminum alloy according to  claim 15 , wherein about 0.14 weight percent zirconium is present in the alloy. 
   
   
       17 . The aluminum alloy according to  claim 16 , wherein about 0.15 weight percent scandium is present in the alloy. 
   
   
       18 . The aluminum alloy according to  claim 16 , wherein about 0.3 weight percent scandium is present in the alloy. 
   
   
       19 . The aluminum alloy according to  claim 16 , wherein about 0.6 weight percent scandium is present in the alloy. 
   
   
       20 . The aluminum alloy according to  claim 16 , wherein about 0.9 weight percent scandium is present in the alloy. 
   
   
       21 . The aluminum alloy according to  claim 16 , wherein from about 2.85 to about 3.0 weight percent magnesium is present in the alloy. 
   
   
       22 . The aluminum alloy according to  claim 15 , wherein the scandium is homogenously distributed throughout the alloy in dispersoids having a diameter of between 15 and 100 nm. 
   
   
       23 . The aluminum alloy according to  claim 15 , wherein the scandium is homogenously distributed throughout the alloy in dispersoids having a diameter of about 15 nm. 
   
   
       24 . An extruded aluminum product formed from the alloy according to  claim 15 . 
   
   
       25 . A cast aluminum billet formed from the alloy according to  claim 15 . 
   
   
       26 . A corrosion resistant and high strength aluminum-magnesium-scandium-zirconium alloy product, the alloy consisting essentially of:
 from 2.2 to 3.0 weight percent magnesium;   from 0.1 to 0.97 weight percent scandium;   from 0.1 to 0.9 weight percent zirconium;   from 0.1 to 0.4 weight percent iron;   from 0.001 to 0.2 weight percent chromium;   from 0.02 to 0.94 weight percent titanium;   up to 0.20 weight percent silicon;   up to 0.1 weight percent copper;   up to 0.1 weight percent zinc; and   up to 0.01 weight percent manganese, the balance being aluminum and incidental impurities.   
   
   
       27 . The aluminum-magnesium-scandium-zirconium alloy product of  claim 26 , wherein the alloy contains up to about 0.91 weight percent scandium. 
   
   
       28 . The aluminum-magnesium-scandium-zirconium alloy product of  claim 27 , wherein the alloy contains about 0.16 to 0.9 weight percent scandium. 
   
   
       29 . The aluminum-magnesium-scandium-zirconium alloy product of  claim 28 , wherein the alloy contains about 0.29 to 0.8 weight percent scandium. 
   
   
       30 . The aluminum-magnesium-scandium-zirconium alloy product of  claim 29 , wherein the alloy contains about 0.45 to 0.75 weight percent scandium. 
   
   
       31 . The aluminum-magnesium-scandium-zirconium alloy product of  claim 30 , wherein the alloy contains about 0.62 to 0.70 weight percent scandium. 
   
   
       32 . The aluminum-magnesium-scandium-zirconium alloy product of  claim 26 , wherein the alloy contains about 2.4 to 3.0 weight percent magnesium. 
   
   
       33 . The aluminum-magnesium-scandium-zirconium alloy product of  claim 32 , wherein the alloy contains about 2.7 to 2.97 weight percent magnesium. 
   
   
       34 . The aluminum-magnesium-scandium-zirconium alloy product of  claim 33 , wherein the alloy contains about 2.8 to 2.95 weight percent magnesium. 
   
   
       35 . The aluminum-magnesium-scandium-zirconium alloy product of  claim 34 , wherein the alloy contains about 2.87 to 2.93 weight percent magnesium. 
   
   
       36 . The aluminum-magnesium-scandium-zirconium alloy product of  claim 26 , wherein the alloy contains about 0.14 to 0.8 weight percent zirconium. 
   
   
       37 . The aluminum-magnesium-scandium-zirconium alloy product of  claim 36 , wherein the alloy contains about 0.3 to 0.7 weight percent zirconium. 
   
   
       38 . The aluminum-magnesium-scandium-zirconium alloy product of  claim 37 , wherein the alloy contains about 0.4 to 0.6 weight percent zirconium. 
   
   
       39 . The aluminum-magnesium-scandium-zirconium alloy product of  claim 26 , wherein the alloy contains about 0.12 to 0.35 weight percent iron. 
   
   
       40 . The aluminum-magnesium-scandium-zirconium alloy product of  claim 39 , wherein the alloy contains about 0.15 to 0.30 weight percent iron. 
   
   
       41 . The aluminum-magnesium-scandium-zirconium alloy product of  claim 40 , wherein the alloy contains about 0.16 to 0.30 weight percent iron. 
   
   
       42 . The aluminum-magnesium-scandium-zirconium alloy product of  claim 26 , wherein the alloy contains about 0.05 to 0.15 weight percent chromium. 
   
   
       43 . The aluminum-magnesium-scandium-zirconium alloy product of  claim 26 , wherein the alloy contains about 0.02 to 0.9 weight percent titanium. 
   
   
       44 . The aluminum-magnesium-scandium-zirconium alloy product of  claim 43 , wherein the alloy contains about 0.03 to 0.7 weight percent titanium. 
   
   
       45 . The aluminum-magnesium-scandium-zirconium alloy product of  claim 26 , wherein the alloy contains up to 0.20 weight percent silicon. 
   
   
       46 . The aluminum-magnesium-scandium-zirconium alloy product of  claim 45 , wherein the alloy contains up to 0.08 weight percent silicon. 
   
   
       47 . The aluminum-magnesium-scandium-zirconium alloy product of  claim 26 , wherein the alloy contains up to 0.09 weight percent copper. 
   
   
       48 . The aluminum-magnesium-scandium-zirconium alloy product of  claim 47 , wherein the alloy contains up to 0.002 weight percent copper. 
   
   
       49 . The aluminum-magnesium-scandium-zirconium alloy product of  claim 26 , wherein the alloy contains up to 0.09 weight percent zinc. 
   
   
       50 . The aluminum-magnesium-scandium-zirconium alloy product of  claim 49 , wherein the alloy contains up to 0.006 weight percent zinc. 
   
   
       51 . The aluminum-magnesium-scandium-zirconium alloy product of  claim 26 , wherein the alloy contains up to 0.009 weight percent manganese. 
   
   
       52 . The aluminum-magnesium-scandium-zirconium alloy product of  claim 51 , wherein the alloy contains up to 0.0032 weight percent manganese. 
   
   
       53 . The aluminum-magnesium-scandium-zirconium alloy product of  claim 26 , wherein the alloy is chill cast in copper molds. 
   
   
       54 . The aluminum-magnesium-scandium-zirconium alloy product of  claim 26 , wherein the product is formed from an extrusion of the alloy. 
   
   
       55 . The aluminum-magnesium-scandium-zirconium alloy product of  claim 54 , wherein the extrusion has a yield strength of 242 MPa and an ultimate tensile strength of 322 MPa. 
   
   
       56 . The aluminum-magnesium-scandium-zirconium alloy product of  claim 55 , wherein the corrosion rate of the extrusion in 3.5% NaCl solution is 0.245 mpy. 
   
   
       57 . The aluminum-magnesium-scandium-zirconium alloy product of  claim 55 , wherein the corrosion rate of the product in impinging aqueous water is 94 mpy when scandium is present at about 0.3 weight percent in the alloy. 
   
   
       58 . The aluminum-magnesium-scandium-zirconium alloy product of  claim 55 , wherein the corrosion rate of the product in impinging aqueous water is 82 mpy when scandium is present at about 0.6 weight percent in the alloy. 
   
   
       59 . The aluminum-magnesium-scandium-zirconium alloy product of  claim 55 , wherein the alloy has a protective layer of boehmite on the alloy's surface, whereby the alloy shows decreased corrosion rate with increased exposure period. 
   
   
       60 . The aluminum-magnesium-scandium-zirconium alloy product of  claim 55 , where the scandium is distributed through the alloy in dispersoids having a diameter of about 15 nm. 
   
   
       61 . The aluminum-magnesium-scandium-zirconium alloy product of  claim 55 , wherein the extrusion exhibits only crystallographic pitting with a maximum pit depth of 30 μm. 
   
   
       62 . The aluminum-magnesium-scandium-zirconium alloy product of  claim 54 , wherein the extrusion has an ultimate tensile strength of up to 325 MPa. 
   
   
       63 . The aluminum-magnesium-scandium-zirconium alloy product of  claim 26 , wherein the product comprises a marine product adapted for use in sea water. 
   
   
       64 . A method for making an aluminum-magnesium-zirconium-scandium alloy, comprising the steps of:
 (a) melting 4N Aluminum in a 60 kg induction furnace at medium frequency (˜2 kHz) in a graphite crucible;   (b) adding Mg-metal, Si-metal, Zr-master alloy and Sc-master alloy to the crucible to form a melt;   (c) mixing and degassing the melt;   (d) analyzing the melt to determine the composition of the melt;   (e) adding material to the melt, when necessary, to correct the composition to: from 2.2 to 3.0 weight percent magnesium, from 0.1 to 0.97 weight percent scandium, from 0.1 to 0.9 weight percent zirconium, from 0.1 to 0.4 weight percent iron, from 0.001 to 0.2 weight percent chromium, from 0.02 to 0.94 weight percent titanium, up to 0.20 weight percent silicon, up to 0.1 weight percent copper, up to 0.1 weight percent zinc, and up to 0.01 weight percent manganese, the balance being aluminum and incidental impurities;   (f) casting the melt at a temperature of 695-705° C. to form billets having a size of about 60 mm×2500 mm;   (g) cutting the billets to a length of about 100mm for extrusion;   (h) homogenizing the cut billets at 590° C. for 14 hours in an indirectly heated electrically powered annealing furnace;   (i) preheating the homogenized billets in an induction furnace to 400° C.;   (j) extruding the preheated billets in a direct 315 MN press to form a flat material; and   (k) cutting the flat material to desired length.