Friction stir fabrication

Abstract

A low-temperature friction-based coating method termed friction stir fabrication (FSF) is disclosed, in which material is deposited onto a substrate and subsequently stirred into the substrate using friction stir processing to homogenize and refine the microstructure. This solid-state process is capable of depositing coatings, including nanocrystalline aluminum and/or metal matrix composites and the like, onto substrates such as aluminum at relatively low temperatures. A method of making rod stock for use in the FSF process is also disclosed.

1 . A method of forming a surface layer on a substrate, the method comprising: 
 depositing a coating material on the substrate; and    friction stirring the deposited coating material.    
     
     
         2 . The method of  claim 1 , wherein the coating material is deposited on the substrate by rotating a tool comprising the coating material against the substrate.  
     
     
         3 . The method of  claim 2 , wherein the tool comprises a solid rod of the coating material.  
     
     
         4 . The method of  claim 3 , wherein the coating material is nanocrystalline.  
     
     
         5 . The method of  claim 3 , wherein the coating material comprises a metal matrix composite.  
     
     
         6 . The method of  claim 5 , wherein the metal matrix composite comprises at least one discontinuous ceramic phase dispersed in the metal matrix.  
     
     
         7 . The method of  claim 6 , wherein the at least one discontinuous ceramic phase comprises a carbide, boride, nitride and/or oxide.  
     
     
         8 . The method of  claim 6 , wherein the discontinuous ceramic phase comprises SiC, TiB 2  and/or Al 2 O 3 .  
     
     
         9 . The method of  claim 5 , wherein the metal matrix comprises Al, Ni, Mg, Ti and/or Fe.  
     
     
         10 . The method of  claim 5 , wherein the metal matrix comprises Al.  
     
     
         11 . The method of  claim 1 , wherein the coating material comprises Al, Ni, Mg, Ti and/or Fe.  
     
     
         12 . The method of  claim 1 , wherein the coating material comprises Al.  
     
     
         13 . The method of  claim 1 , wherein the substrate comprises a metal.  
     
     
         14 . The method of  claim 1 , wherein the substrate comprises Al.  
     
     
         15 . The method of  claim 1 , wherein the step of depositing the coating material on the substrate is performed at a temperature below a melting temperature of the coating material.  
     
     
         16 . The method of  claim 1 , wherein the coating material is deposited on the substrate in solid form.  
     
     
         17 . The method of  claim 1 , wherein the coating material comprises Al and is deposited on the substrate at a temperature below about 500°.  
     
     
         18 . The method of  claim 17 , wherein the coating material is deposited on the substrate at a temperature below about 400° C.  
     
     
         19 . The method of  claim 1 , wherein the step of friction stirring is performed with a substantially non-consumable rotating tool.  
     
     
         20 . The method of  claim 19 , wherein the step of friction stirring includes multiple passes of the rotating tool across a surface of the substrate.  
     
     
         21 . The method of  claim 1 , wherein the step of friction stirring is performed at a temperature below a melting temperature of the coating material.  
     
     
         22 . The method of  claim 1 , wherein the step of friction stirring is performed at a temperature below a melting temperature of the substrate.  
     
     
         23 . The method of  claim 1 , wherein the substrate comprises aluminum and the step of friction stirring is performed at a temperature below about 500° C.  
     
     
         24 . The method of  claim 23 , wherein the coating material comprises aluminum and has a nanocrystalline structure after the friction stirring.  
     
     
         25 . A substrate having a surface layer formed by the method of  claim 1 .  
     
     
         26 . A method of filling a hole in a substrate, the method comprising: 
 placing powder of a fill material in the hole; and    friction stirring the fill material powder in the hole to consolidate the fill material.    
     
     
         27 . The method of  claim 26 , wherein the step of friction stirring is performed at a temperature below a melting temperature of the fill material.  
     
     
         28 . The method of  claim 26 , wherein the step of friction stirring is performed at a temperature below a melting temperature of the substrate.  
     
     
         29 . The method of  claim 26 , further comprising: 
 placing additional powder of a fill material in the hole after the step of friction stirring; and    friction stirring the additional fill material powder in the hole to consolidate the additional fill material powder.    
     
     
         30 . The method of  claim 29 , wherein the fill material powder and the additional fill material powder are the same composition.  
     
     
         31 . The method of  claim 29 , wherein the fill material powder and the additional fill material powder are different compositions.  
     
     
         32 . The method of  claim 26 , wherein the consolidated fill material is nanocrystalline.  
     
     
         33 . The method of  claim 26 , wherein the consolidated fill material comprises a metal matrix composite.  
     
     
         34 . A method of making consumable friction stirring rod stock, the method comprising: 
 placing powder of a coating material in a die;    friction stirring the coating material powder in the die to consolidate the coating material; and    recovering a rod comprising the consolidated coating material.    
     
     
         35 . The method of  claim 34 , wherein the step of friction stirring is performed at a temperature below a melting temperature of the coating material.  
     
     
         36 . The method of  claim 34 , further comprising: 
 placing additional powder of a coating material in the die after the step of friction stirring; and    friction stirring the additional coating material powder in the die to consolidate the additional coating material powder.    
     
     
         37 . The method of  claim 36 , wherein the coating material powder and the additional coating material powder are the same composition.  
     
     
         38 . The method of  claim 36 , wherein the coating material powder and the additional coating material powder are different compositions.