Aluminum alloys with grain refiners, and methods for making and using the same

Abstract

We have developed a scalable approach to directly incorporate grain-refining nanoparticles into conventional hot-tear-susceptible aluminum alloy powders. These aluminum alloy powders may be additively manufactured into high-strength, crack-free aluminum alloys with fine equiaxed microstructures by incorporating nanoparticle nucleants to control solidification during additive manufacturing. Some variations provide an additively manufactured aluminum alloy comprising aluminum, one or more strengthening elements, and at least one grain-refining element, wherein the additively manufactured aluminum alloy has a microstructure with equiaxed grains. Aluminum alloys with grain refiners are useful in many processes beyond additive manufacturing. Some variations provide an aluminum alloy comprising aluminum, copper, magnesium, at least one of zinc or silicon, and grain-refining nanoparticles selected from zirconium, tantalum, niobium, or titanium, wherein the aluminum alloy has a microstructure that is substantially crack-free with equiaxed grains.

What is claimed is: 
     
         1 . An aluminum alloy comprising:
 (a) at least 80 wt % aluminum;   (b) copper;   (c) magnesium;   (d) at least one of zinc or silicon; and   (e) grain-refining nanoparticles comprising an element selected from the group consisting of zirconium, tantalum, niobium, titanium, and oxides, nitrides, hydrides, carbides, borides, or aluminides thereof, and combinations of any of the foregoing,   wherein said aluminum alloy has a microstructure that is substantially crack-free with equiaxed grains.   
     
     
         2 . The aluminum alloy of  claim 1 , wherein said copper is present in a concentration from about 0.1 wt % to about 10 wt %. 
     
     
         3 . The aluminum alloy of  claim 1 , wherein said magnesium is present in a concentration from about 0.1 wt % to about 10 wt %. 
     
     
         4 . The aluminum alloy of  claim 1 , wherein said at least one of zinc or silicon is present in a concentration from about 0.1 wt % to about 10 wt %. 
     
     
         5 . The aluminum alloy of  claim 1 , wherein said grain-refining nanoparticles are present in a concentration of at least 0.01 vol %. 
     
     
         6 . The aluminum alloy of  claim 5 , wherein said grain-refining nanoparticles are present in a concentration of at least 0.1 vol %. 
     
     
         7 . The aluminum alloy of  claim 6 , wherein said grain-refining nanoparticles are present in a concentration of at least 1 vol %. 
     
     
         8 . The aluminum alloy of  claim 7 , wherein said grain-refining nanoparticles are present in a concentration of at least 5 vol %. 
     
     
         9 . The aluminum alloy of  claim 1 , wherein said aluminum alloy further comprises chromium. 
     
     
         10 . The aluminum alloy of  claim 1 , wherein said aluminum alloy comprises zinc, and wherein said grain-refining nanoparticles comprise an element selected from the group consisting of zirconium, tantalum, niobium, and oxides, nitrides, hydrides, carbides, borides, or aluminides thereof, and combinations of any of the foregoing. 
     
     
         11 . The aluminum alloy of  claim 1 , wherein said aluminum alloy comprises silicon, and wherein said grain-refining nanoparticles comprise an element selected from the group consisting of zirconium, tantalum, niobium, and oxides, nitrides, hydrides, carbides, borides, or aluminides thereof, and combinations of any of the foregoing. 
     
     
         12 . The aluminum alloy of  claim 1 , wherein said aluminum alloy consists essentially of Al 7075 alloy in combination with said grain-refining nanoparticles. 
     
     
         13 . The aluminum alloy of  claim 1 , wherein said aluminum alloy consists essentially of Al 6061 alloy in combination with said grain-refining nanoparticles. 
     
     
         14 . The aluminum alloy of  claim 1 , wherein said aluminum alloy has a tensile strength of at least 400 MPa. 
     
     
         15 . The aluminum alloy of  claim 1 , wherein said aluminum alloy is substantially free of porous defects. 
     
     
         16 . An additively manufactured aluminum alloy comprising:
 (a) at least 80 wt % aluminum;   (b) at least one strengthening element selected from the group consisting of zinc, silicon, copper, magnesium, lithium, silver, titanium, chromium, manganese, iron, vanadium, bismuth, gallium, lead, and combinations thereof; and   (c) at least one grain-refining element selected from the group consisting of zirconium, tantalum, niobium, titanium, boron, tungsten, carbon, and oxides, nitrides, hydrides, carbides, borides, or aluminides thereof, and combinations of any of the foregoing,   wherein said additively manufactured aluminum alloy has a microstructure with equiaxed grains.   
     
     
         17 . The additively manufactured aluminum alloy of  claim 16 , wherein said at least one strengthening element is present in a concentration from about 0.01 wt % to about 20 wt %. 
     
     
         18 . The additively manufactured aluminum alloy of  claim 16 , wherein said at least one grain-refining element is selected from the group consisting of Al 3 Zr, Al 3 Ta, Al 3 Nb, Al 3 Ti, TiB, TiB 2 , WC, AlB, and combinations thereof. 
     
     
         19 . The additively manufactured aluminum alloy of  claim 16 , wherein said at least one grain-refining element is in the form of nanoparticles. 
     
     
         20 . The additively manufactured aluminum alloy of  claim 16 , wherein said at least one grain-refining element is lattice-matched to within ±5% compared to an alloy of said aluminum and said at least one strengthening element. 
     
     
         21 . The additively manufactured aluminum alloy of  claim 20 , wherein said at least one grain-refining element is lattice-matched to within ±0.5% compared to an alloy of said aluminum and said at least one strengthening element. 
     
     
         22 . The additively manufactured aluminum alloy of  claim 16 , wherein said at least one grain-refining element is atomic density-matched to within ±25% compared to an alloy of said aluminum, said at least one strengthening element, and optionally an additional particulate. 
     
     
         23 . The additively manufactured aluminum alloy of  claim 16 , wherein said aluminum alloy is characterized by an average grain size of less than 1 millimeter. 
     
     
         24 . The additively manufactured aluminum alloy of  claim 23 , wherein said aluminum alloy is characterized by an average grain size of less than 10 microns. 
     
     
         25 . The additively manufactured aluminum alloy of  claim 24 , wherein said aluminum alloy is characterized by an average grain size of less than 0.1 microns. 
     
     
         26 . The additively manufactured aluminum alloy of  claim 16 , wherein said microstructure is substantially crack-free. 
     
     
         27 . The additively manufactured aluminum alloy of  claim 16 , wherein said additively manufactured aluminum alloy has a tensile strength of at least 400 MPa. 
     
     
         28 . The additively manufactured aluminum alloy of  claim 16 , wherein said microstructure is substantially free of porous void defects. 
     
     
         29 . The additively manufactured aluminum alloy of  claim 16 , wherein said microstructure has a crystallographic texture that is not solely oriented in an additive-manufacturing build direction. 
     
     
         30 . The additively manufactured aluminum alloy of  claim 16 , wherein said microstructure contains a plurality of dendrite layers having differing primary growth-direction angles with respect to each other.