Aluminum 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 pure aluminum or aluminum alloy powders. These aluminum alloy powders may be additively manufactured into high-strength, crack-free aluminum alloys with fine equated microstructures by incorporating nanoparticle nucleants to control solidification during additive manufacturing. Some variations provide an additively manufactured aluminum alloy comprising aluminum and at least one grain-refining element, wherein the additively manufactured aluminum alloy has a microstructure with equated grains. Pure aluminum or aluminum alloys, combined with grain refiners, are useful in many processes beyond additive manufacturing. Some variations provide an aluminum alloy comprising aluminum and grain-refining nanoparticles selected from zirconium, tantalum, niobium, or titanium, wherein the aluminum alloy has a microstructure that is substantially crack-free with equated grains.

What is claimed is: 
     
         1 . An aluminum alloy powder for manufacturing a three-dimensional high-strength aluminum alloy part by a powder bed fusion additive manufacturing process, each particle of the aluminum alloy powder comprising:
 an aluminum alloy including silicon, copper, and optionally magnesium,   wherein, when said aluminum alloy is heated to a first temperature greater than a liquidus temperature of said aluminum alloy and subsequently cooled to a second temperature less than said liquidus temperature of said aluminum alloy and greater than a solidus temperature of said aluminum alloy, said aluminum alloy transitions from a liquid phase to a multiphase system that includes a solution of liquid phase aluminum and a solid phase of silicon particles dispersed throughout said liquid phase aluminum.   
     
     
         2 . The aluminum alloy powder of  claim 1 , wherein said copper is present in a concentration from about 0.1 wt % to about 10 wt % in said aluminum alloy. 
     
     
         3 . The aluminum alloy powder of  claim 1 , wherein said copper is present in a concentration from about 2 wt % to about 5 wt % in said aluminum alloy. 
     
     
         4 . The aluminum alloy powder of  claim 1 , wherein said copper is present in a concentration from about 3 wt % to about 4 wt % in said aluminum alloy. 
     
     
         5 . The aluminum alloy powder of  claim 1 , wherein said magnesium is present in a concentration from 0 wt % to about 2 wt % in said aluminum alloy. 
     
     
         6 . The aluminum alloy powder of  claim 1 , wherein said magnesium is present in a concentration from about 0.5 wt % to about 1 wt % in said aluminum alloy. 
     
     
         7 . The aluminum alloy powder of  claim 1 , wherein said magnesium is present in a concentration from about 0.01 wt % to about 10 wt % in said aluminum alloy. 
     
     
         8 . The aluminum alloy powder of  claim 1 , wherein said silicon is present in a concentration from about 0.01 wt % to about 20 wt % in said aluminum alloy. 
     
     
         9 . The aluminum alloy powder of  claim 1 , wherein said silicon is present in a concentration from about 0.1 wt % to about 10 wt % in said aluminum alloy. 
     
     
         10 . The aluminum alloy powder of  claim 1 , wherein said silicon is present in a concentration from about 13 wt % to about 20 wt % in said aluminum alloy. 
     
     
         11 . The aluminum alloy powder of  claim 1 , wherein said aluminum alloy further includes greater than 0 wt % and up to about 9 wt % iron, and wherein said multiphase system includes said solution of liquid phase aluminum, said solid phase of silicon particles, and another solid phase of iron-containing intermetallic particles dispersed throughout said liquid phase aluminum. 
     
     
         12 . The aluminum alloy powder of  claim 1 , wherein said aluminum alloy further includes greater than 0 wt % and up to about 5 wt % manganese. 
     
     
         13 . An aluminum alloy powder for manufacturing a three-dimensional high-thermal-conductivity aluminum alloy part by a powder-bed-fusion additive manufacturing process, each particle of said aluminum alloy powder comprising:
 an aluminum alloy including, by weight:
 greater than 95% aluminum, and 
 greater than 0% and less than 5% of at least one nucleating agent, 
   wherein, when said aluminum alloy is heated to a first temperature greater than a liquidus temperature of said aluminum alloy and subsequently cooled to a second temperature less than said liquidus temperature of said aluminum alloy and greater than a solidus temperature of said aluminum alloy, said aluminum alloy transitions from a liquid phase to a multiphase system, and   wherein said multiphase system includes a solution of liquid phase aluminum and a solid phase of particles of said at least one nucleating agent dispersed throughout said liquid phase aluminum.   
     
     
         14 . A method of manufacturing a three-dimensional aluminum alloy part, said method comprising:
 (a) providing an aluminum alloy powder feed material;   (b) distributing a layer of said powder feed material over a substrate;   (c) scanning selective regions of said layer of said powder feed material with a high-energy laser or electron beam to form a pool of molten aluminum alloy material therein, wherein selective regions of said layer of said powder feed material corresponding to a cross-section of an aluminum alloy part being formed;   (d) terminating said laser or electron beam to cool and solidify said pool of molten aluminum alloy material into a solid layer of fused aluminum alloy material; and   (e) sequentially repeating steps (b) through (d) to form said aluminum alloy part made up of a plurality of solid layers of fused aluminum alloy material,   wherein, during solidification of said pool of molten aluminum alloy material, solid-phase particles form within a solution of liquid phase aluminum prior to formation of solid-phase aluminum dendrites, and   wherein, each of said solid layers of fused aluminum alloy material in said aluminum alloy part includes a continuous aluminum matrix phase that exhibits a crystalline structure and predominantly includes a plurality of equiaxed grains.   
     
     
         15 . The method of  claim 14 , wherein, during solidification of said pool of molten aluminum alloy material, said molten aluminum alloy material transitions from an entirely liquid phase to a multiphase system in which said solid-phase particles are dispersed throughout said solution of liquid phase aluminum. 
     
     
         16 . The method of  claim 14 , wherein said solid-phase particles serve as nuclei for subsequent formation of said solid-phase aluminum dendrites, and wherein, after said solid-phase particles form within said solution of liquid phase aluminum, said solid-phase aluminum dendrites nucleate and grow in multiple directions on said solid-phase particles. 
     
     
         17 . The method of  claim 16 , wherein growth of said solid-phase aluminum dendrites is arrested when neighboring aluminum dendrites impinge upon one another and form grain boundaries. 
     
     
         18 . The method of  claim 14 , wherein each particle of said aluminum alloy powder feed material comprises silicon, and wherein said solid-phase particles comprise particles of silicon. 
     
     
         19 . The method of  claim 18 , wherein said aluminum alloy powder feed material comprises silicon comprises from about 0.01 wt % to about 20 wt % silicon. 
     
     
         20 . The method of  claim 19 , wherein said aluminum alloy powder further comprises:
 greater than 0 wt % and up to 9 wt % iron;   greater than 0 wt % and up to 5 wt % manganese; and   silicon,   wherein said solid-phase particles comprise intermetallic particles.   
     
     
         21 . The method of  claim 19 , wherein each particle of said aluminum alloy powder feed material further comprises:
 from about 0.1 wt % to about 10 wt % copper; and   from 0 wt % to about 2 wt % magnesium.   
     
     
         22 . The method of  claim 14 , wherein each particle of said aluminum alloy powder feed material comprises, by weight:
 greater than 95% aluminum, and   greater than 0% and less than 5% of at least one nucleating agent.   
     
     
         23 . The method of  claim 14 , wherein said at least one nucleating agent comprises at least one element or compound of titanium (Ti), boron (B), beryllium (Be), cobalt (Co), chromium (Cr), cesium (Cs), iron (Fe), hafnium (Hf), manganese (Mn), molybdenum (Mo), niobium (Nb), lead (Pb), sulfur (S), zirconium (Zr), scandium (Sc), selenium (Se), strontium (Sr), tantalum (Ta), vanadium (V), or tungsten (W). 
     
     
         24 . The method of  claim 23 , wherein said aluminum alloy powder feed material comprises greater than 0.1 wt % and less than 5 wt % Ti.