High-temperature high-strength aluminum alloys processed through the amorphous state

Abstract

Aluminum alloys having improved strength at 300° C. characterized by formation from an intermediate amorphous state to a final fcc matrix hardened by optimal 25 nm-diameter Ll 2 precipitates with an interphase misfit less than about 4% in all three dimensions and Al 23 Ni 6 M 4 precipitates where M is one or more elements selected from the group consisting of Y and Yb. An appropriate melt of aluminum with selected transition metals (Co, Cu, Fe, Ni, Ti, Y) and Ll 2 stabilizers (Sc, Yb) in amounts of about 2 to 12 and 2 to 15 atomic percent, respectively, is processed to achieve an intermediate amorphous state to dissolve Ll 2 -forming components. The amorphous alloys are then thermo-mechanically devitrified to a final crystalline microstructure. The alloys have good ductility and a short-term tensile strength exceeding about 275 MPa (40 ksi) at 300° C., and are useful for applications such as high-temperature turbine engine components or aircraft structural components.

1 . An aluminum alloy characterized by high strength iii the temperature range greater than about 300° C. comprising, in combination:
 an alloy mixture in primarily crystalline form having at least about 70% by volume fcc phase, at least about 110% by volume Ll 2  precipitate phase, and at least about 10% by volume Al 23 Ni 6 M 4  precipitate phase where M is one or more elements selected from the group consisting of Y and Yb, said alloy consisting essentially of one or more transition metals selected from the group consisting of about 2 to 12 atomic percent Co, Cu, Fe, Ni, Ti, and Y; and one or more elements comprising said Ll 2  phase selected from the group consisting of about 2 to 15 atomic percent Sc and Yb; optionally of transition metals selected from the group consisting of Cr, Li, Mn, V, and Zn, and the balance Al and incidental elements and impurities; said Ll 2  phase in the form of a precipitate particle dispersion having a particle diameter of less than about 80 nm.   
     
     
         2 . The alloy of  claim 1  having a tensile yield strength of at least about 275 MPa at 300° C. 
     
     
         3 . An aluminum alloy characterized by high strength at a temperature greater than about 300° C. made by a process comprising the steps of:
 (a) formulating a melt comprised of Al; at least one transition metal selected from the group consisting of Co, Cu, Fe, Ni, Ti and Y; at least one element selected from the Ll 2 -stabilizing element group consisting of Sc and Yb; optionally of transition metals selected from the group consisting of Cr, Li, Mn, V, and Zn;   (b) converting the melt to at least about 70% by volume amorphous material; and   (c) devitrifying, at least in part, the amorphous material to a mixture of Ll 2  crystalline rare earth precipitate phase material in a particle dispersion wherein the particle size is less than about 80 nm, Al 23 Ni 6 M 4  precipitate phase where M is one or more elements selected from the group consisting of Y and Yb, and fcc phase material.   
     
     
         4 . The alloy product by the process of  claim 3  wherein the transition metal is provided in an amount of about 2 to 12 atomic percent. 
     
     
         5 . The alloy product by the process of  claim 3  wherein the Ll 2 -stabilizing element is provided in an amount of about 2 to 10 atomic percent. 
     
     
         6 . The alloy product by the process of  claim 3  wherein devitrifying the amorphous material comprises forming at least about 70% by volume fcc phase. 
     
     
         7 . The alloy product by the process of  claim 3  wherein devitrifying the amorphous material comprises forming at least 10% by volume Ll 2  phase in partial form. 
     
     
         8 . The alloy product by the process of  claim 3  wherein devitrifying the amorphous material comprises forming at least 10% by volume Al 23 Ni 6 M 4  phase in partial form, where M is one or more elements selected; from the group consisting of Y and Yb. 
     
     
         9 . The alloy product by the process of  claim 3  wherein converting the melt to amorphous material comprises at least one step selected from the group consisting of gas powder atomization, water powder atomization and melt spinning. 
     
     
         10 . The alloy product by the process of  claim 3  wherein, devitrification comprises at least one step selected from the group consisting of hot isostatic pressing, thermal aging, and extrusion. 
     
     
         11 . The product by the process of  claim 3  wherein converting the melt comprises rapid solidification processing. 
     
     
         12 . An aluminum alloy consisting essentially of about 2-12 atomic percent of at least one transition element selected from the group consisting of Co, Cu, Fe, Ni, Ti, and Y; about 2-15 atomic percent of at least one element selected from the group consisting, of Yb and Sc; optionally of transition metals selected from the group consisting of Cr, Li, Mn, V, and Zn; and the balance Al and incidental elements and impurities characterized by greater than about 70% crystalline microstructure with a dispersion of Ll 2  phase particles greater than 10% by volume and Al 23 Ni 6 M 4  phase particles greater than 10% by volume, where M is one or more elements selected from the group consisting of Y and Yb, in a matrix of greater than 70% by volume fcc phase generated by a rapid solidification process from a substantially amorphous vitrified phase, said particle diameter of said Ll 2  particles in the range of about 1.0 to 80 nm. 
     
     
         13 . The alloy of  claim 12  wherein the nominal particle diameter of the Ll 2  particles is about 25 nm. 
     
     
         14 . The alloy of  claim 12 , consisting essentially of about 0.7 atomic % Co, 3.5 atomic % Ni, and at least one element selected from the group consisting of Sc and Yb. 
     
     
         15 . The alloy of  claim 12  consisting essentially of about 0.7 atomic % Co, about 3.5 atomic % Ni, and Sc, Ti, Y, Yb, and Zr, cumulatively in the range of about 4 to 8 atomic %.