High strength l12 aluminum alloys produced by cryomilling

Abstract

A method and apparatus produces high strength aluminum alloys from a cryomilled powder containing L1 2 intermetallic dispersoids. The cryomilled powder is degassed, sealed under vacuum in a container, heated, consolidated by vacuum hot pressing, and extruded.

1 . A method for producing a high strength aluminum alloy billet containing L1 2  dispersoids, comprising the steps of:
 cryomilling a quantity of an aluminum alloy powder containing an L1 2  dispersoid therein to produce a mesh size of less than −325 mesh;   placing the cryomilled powder in a container;   vacuum degassing the powder at a temperature of about 500° F. (260° C.) to about 900° F. (482° C.) for about 12 hours to about 8 days;   sealing the degassed powder in the container under vacuum;   heating the sealed container at about 700° F. (371° C.) to about 900° F. (482° C.) for about one to eight hours;   vacuum hot pressing the heated container to form a billet; and   removing the container from the formed billet.   
     
     
         2 . The method of  claim 1 , wherein the container is aluminum having a central axis, and vacuum hot pressing is done along the axis while restraining radial movement of the container. 
     
     
         3 . The method of  claim 1 , wherein the vacuum hot pressing includes blind die compaction for about 1 hour to about 8 hours at a temperature of 700° F. (371° C.) to about 900° F. (482° C.) under uni-axial pressure of about 20 ksi (138 Mpa) to about 100 ksi (690 MPa). 
     
     
         4 . The method of  claim 1 , wherein the vacuum hot pressing produces a billet of the aluminum alloy powder having a theoretical density of about 100 percent. 
     
     
         5 . The method of  claim 1 , wherein the degassing includes rotating the aluminum alloy powder to heat and expose all the powder to vacuum. 
     
     
         6 . The method of  claim 1 , wherein the thus formed billet is extruded at a pressure of about 20 ksi (138 Mpa) to about 100 ksi (690 MPa). 
     
     
         7 . The method of  claim 6 , wherein the extrusion temperature is about 300° F. (149° C.) to about 850° F. (454° C.), the billet soak time is about 0.5 hours to about 8 hours at a rate of about 0.2 inch per minute (0.51 cm per minute) to about 10 inch per minute (25.4 cm per minute), and an extrusion ratio of about 2:1 to about 40:1. 
     
     
         8 . The method of  claim 1 , wherein the L1 2  dispersoids comprise Al 3 X dispersoids wherein X is at least one first element selected from the group comprising:
 about 0.1 to about 4.0 weight percent scandium, about 0.1 to about 20.0 weight percent erbium, about 0.1 to about 15.0 weight percent thulium, about 0.1 to about 25.0 weight percent ytterbium, and about 0.1 to about 25.0 weight percent lutetium;   at least one second element selected from the group comprising about 0.1 to about 20.0 weight percent gadolinium, about 0.1 to about 20.0 weight percent yttrium, about 0.05 to about 4.0 weight percent zirconium, about 0.05 to about 10.0 weight percent titanium, about 0.05 to about 10.0 weight percent hafnium, and about 0.05 to about 5.0 weight percent niobium; and   the balance substantially aluminum.   
     
     
         9 . The method of  claim 8 , wherein the aluminum alloy powder contains at least one third element selected from the group consisting of silicon, magnesium, lithium, copper, zinc, and nickel. 
     
     
         10 . The method of  claim 9 , wherein the third element comprises at least one of about 4 to about 25 weight percent silicon, about 1 to about 8 weight percent magnesium, about 0.5 to about 3 weight percent lithium, about 0.2 to about 3 weight percent copper, about 3 to about 12 weight percent zinc, about 1 to about 12 weight percent nickel. 
     
     
         11 . The method of  claim 8 , wherein the L1 2  dispersoids comprise Al 3 X dispersoids wherein X is at least one first element selected from the group comprising:
 about 0.1 to about 0.5 weight percent scandium, about 0.1 to about 6.0 weight percent erbium, about 0.1 to about 10.0 weight percent thulium, about 0.1 to about 15.0 weight percent ytterbium, and about 0.1 to about 12.0 weight percent lutetium;   at least one second element selected from the group comprising about 0.1 to about 4.0 weight percent gadolinium, about 0.1 to about 4.0 weight percent yttrium, about 0.05 to about 1.0 weight percent zirconium, about 0.05 to about 2.0 weight percent titanium, about 0.05 to about 2.0 weight percent hafnium, and about 0.05 to about 1.0 weight percent niobium; and   the balance substantially aluminum.   
     
     
         12 . A method for producing a high strength aluminum alloy billet containing L1 2  dispersoids, comprising the steps of:
 sieving a quantity of an aluminum alloy powder containing an L1 2  dispersoid therein to produce a particle size of less than 100 mesh;   blending the sieved aluminum alloy powder to homogenize the particle size distribution;   cryomilling the blended aluminum alloy powder containing an L1 2  dispersoid therein to produce a mesh size of less than −325 mesh; and   compacting the cryomilled powder to form a billet.   
     
     
         13 . The method of  claim 12 , wherein the cryomilled powder is placed in a container, vacuum degassed at a temperature of about 500° F. (260° C.) to about 900° F. (482° C.) for about 12 hours to about 8 days; followed by sealing the degassed powder in the container under vacuum and heating the sealed container at about 700° F. (371° C.) to about 900° F. (482° C.) for about one to eight hours. 
     
     
         14 . The method of  claim 13 , which further includes the step of vacuum hot pressing the heated container to form a billet; and removing the container from the formed billet. 
     
     
         15 . The method of  claim 14 , wherein the vacuum hot pressing produces a billet of the aluminum alloy powder having a density of about 100 percent. 
     
     
         16 . The method of  claim 13 , wherein the degassing includes rotating the aluminum alloy powder to heat and exposing to vacuum all the powder. 
     
     
         17 . The method of  claim 12 , wherein the formed billet is extruded at a pressure of about 20 ksi (138 MPA) to about 100 ksi (690 MPa). 
     
     
         18 . The method of  claim 17 , wherein the extrusion temperature is about 300° F. (149° C.) to about 850° F. (454° C.), the billet soak time is about 0.5 hours to about 8 hours at a rate of about 0.2 inch per minute (0.51 cm per minute) to about 10 inch per minute (25.4 cm per minute), and an extrusion ratio of about 2:1 to about 40:1. 
     
     
         19 . The method of  claim 12 , wherein the L1 2  dispersoids comprise Al 3 X dispersoids wherein X is at least one first element selected from the group comprising:
 about 0.1 to about 4.0 weight percent scandium, about 0.1 to about 20.0 weight percent erbium, about 0.1 to about 15.0 weight percent thulium, about 0.1 to about 25.0 weight percent ytterbium, and about 0.1 to about 25.0 weight percent lutetium;   at least one second element selected from the group comprising about 0.1 to about 20.0 weight percent gadolinium, about 0.1 to about 20.0 weight percent yttrium, about 0.05 to about 4.0 weight percent zirconium, about 0.05 to about 10.0 weight percent titanium, about 0.05 to about 10.0 weight percent hafnium, and about 0.05 to about 5.0 weight percent niobium; and   the balance substantially aluminum.   
     
     
         20 . The method of  claim 19 , wherein the third element comprises at least one of about 4 to about 25 weight percent silicon, about 1 to about 8 weight percent magnesium, about 0.5 to about 3 weight percent lithium, about 0.2 to about 3 weight percent copper, about 3 to about 12 weight percent zinc, about 1 to about 12 weight percent nickel. 
     
     
         21 . A high strength aluminum alloy billet comprising:
 aluminum alloy matrix; and   dispersoids within the aluminum matrix wherein X is at least one first element selected from the group consisting of:   about 0.1 to about 4.0 weight percent scandium, about 0.1 to about 20.0 weight percent erbium, about 0.1 to about 15.0 weight percent thulium, about 0.1 to about 25.0 weight percent ytterbium, and about 0.1 to about 25.0 weight percent lutetium;   at least one second element selected from the group consisting of about 0.1 to about 20.0 weight percent gadolinium, about 0.1 to about 20.0 weight percent yttrium, about 0.05 to about 4.0 weight percent zirconium, about 0.05 to about 10.0 weight percent titanium, about 0.05 to about 10.0 weight percent hafnium, and about 0.05 to about 5.0 weight percent niobium; and   at least one selected from the group consisting of about 4 to about 25 weight percent silicon, about 1 to about 8 weight percent magnesium, about 0.5 to about 3 weight percent lithium, about 0.2 to about 3 weight percent copper, about 3 to about 12 weight percent zinc, about 1 to about 12 weight percent nickel;   wherein the billet dorsile strength of at least 100 ksi (690 MPa) and a yield strength of at least 95 ksi (655 MPa).