Aluminum superalloys for use in high temperature applications

Abstract

Aluminum-zirconium and aluminum-zirconium-lanthanide superalloys are described that can be used in high temperature, high stress and a variety of other applications. The lanthanide is preferably holmium, erbium, thulium or ytterbium, most preferably erbium. Also, methods of making the aforementioned alloys are disclosed. The superalloys, which have commercially-suitable hardness at temperatures above about 220° C., include nanoscale Al 3 Zr precipitates and optionally nanoscale Al 3 Er precipitates and nanoscale Al 3 (Zr,Er) precipitates that create a high-strength alloy capable of withstanding intense heat conditions. These nanoscale precipitates have a L1 2 -structure in α-Al(f.c.c.) matrix, an average diameter of less than about 20 nanometers (“nm”), preferably less than about 10 nm, and more preferably about 4-6 nm and a high number density, which for example, is larger than about 10 21 m −3 , of the nanoscale precipitates. The formation of the high number density of nanoscale precipitates is thought to be due to the addition of inoculant, such as a Group 3A, 4A, and 5A metal or metalloid. Additionally, methods for increasing the diffusivity of Zr in Al are disclosed.

1 - 51 . (canceled) 
     
     
         52 . A method of forming an essentially scandium-free aluminum alloy having a nanoscale precipitate comprising Al 3 Zr having a L1 2 -structure, the method comprising:
 (a) making a melt of aluminum and an addition of zirconium, and one or more of erbium, silicon, tin, indium, antimony, and magnesium;   (b) solidifying the melt and cooling the resulting solid piece to a temperature of about 0° C. to about 300° C.   
     
     
         53 . The method of forming an essentially scandium free aluminum alloy of  claim 52 , further comprising:
 (c) homogenizing the solid piece at a temperature of about 600° C. to about 660° C. for about 0.3 hour to about 72 hours.   
     
     
         54 . The method of forming an essentially scandium free aluminum alloy of  claim 52 , further comprising:
 (d) performing a first heat-treating step by maintaining a temperature of about 100° C. to about 375° C. for about 1 to about 12 hours.   
     
     
         55 . The method of forming as essentially scandium free aluminum alloy of  claim 52 , further comprising:
 (e) performing a main heat treating step that comprises heating and maintaining a temperature of about 375° C. to about 550° C. for about 1 hour to 48 hours.   
     
     
         56 . The method of forming an essentially scandium-free aluminum alloy of  claim 52  wherein the nanoscale precipitate comprises Al 3 Zr, Al 3 Er and Al 3 (Zr,Er). 
     
     
         57 . The method of forming an essentially scandium free aluminum alloy of  claim 56 , further comprising:
 (c) homogenizing the solid piece at a temperature of about 600° C. to about 660° C. for about 0.3 hour to about 72 hours.   
     
     
         58 . The method of forming an essentially scandium free aluminum alloy of  claim 56 , further comprising:
 (d) performing a first heat-treating step by maintaining a temperature of about 100° C. to about 375° C. for about 1 to about 12 hours.   
     
     
         59 . The method of forming as essentially scandium free aluminum alloy of  claim 56 , further comprising:
 (e) performing a main heat treating step that comprises heating and maintaining a temperature of about 375° C. to about 550° C. for about 1 hour to 48 hours.