Free-machining aluminum alloy

Abstract

Various illustrative embodiments of a free-machining aluminum alloy composition and related methods are provided. The aluminum alloy composition can include an aluminum alloy and an effective amount of a graphitic material as a free-machining constituent. Free-machining means the graphitic material is capable of modifying the machining character of the aluminum alloy by affecting the generation of chip-shaped machining debris and/or the friction between the machining tool and the workpiece.

1 . An aluminum alloy composition comprising: an aluminum alloy; and boron nitride as a free machining constituent. 
     
     
         2 . The aluminum alloy composition of  claim 1 , wherein the aluminum alloy is AA 6061. 
     
     
         3 . The aluminum alloy composition of  claim 1 , wherein the amount of boron nitride in the composition is greater than 0.25% by weight. 
     
     
         4 . The aluminum alloy composition of  claim 1 , wherein the composition is essentially heavy metal free. 
     
     
         5 . The aluminum alloy composition of  claim 1 , wherein the boron nitride has a particle size in the range from 5-150 microns. 
     
     
         6 . The aluminum alloy composition of  claim 1 , consisting essentially of, in approximate weight %:
 from 0.25-2.5% boron nitride;   from 0.5 to 2.0% magnesium;   from 0.5 to 2.0% silicon;   from zero to 2.0% copper;   from zero to 1.0% manganese;   and the balance being aluminum, incidental elements and impurities.   
     
     
         7 . The aluminum alloy composition of  claim 1  wherein the boron nitride composition is greater than 3.0% by weight and is used as a master alloy. 
     
     
         8 . A free machining, essentially heavy metal free aluminum alloy composition comprising: an aluminum alloy; and boron nitride in a weight % in the alloy composition such that the alloy composition exhibits reduced workpiece/tool friction during machining and promotes the generation of small chip-like machining debris. 
     
     
         9 . An aluminum alloy composition comprising: an aluminum alloy; and a graphitic material as a free machining constituent. 
     
     
         10 . The aluminum alloy composition of  claim 9 , wherein the graphitic material comprises boron nitride. 
     
     
         11 . The aluminum alloy composition of  claim 9 , wherein the graphitic material comprises one or more materials from the group consisting from graphite, boron nitride, molybdenum disulfide and tungsten disulfide. 
     
     
         12 . A method of improving the free machining properties of an aluminum alloy comprising: providing a molten aluminum alloy; adjusting the composition of the molten aluminum alloy by adding an effective amount of boron nitride so that the boron nitride occupies greater than 0.25% by weight of the alloy; and solidifying the alloy so that the alloy is capable of being machined into a machined article. 
     
     
         13 . A method of making an aluminum alloy material, the method comprising:
 providing a molten aluminum alloy; adding graphitic particles to the molten aluminum alloy; dispersing the graphitic particles in the molten aluminum alloy; and forming the molten aluminum alloy into a solidified aluminum alloy material.   
     
     
         14 . The method of  claim 13 , further comprising ultrasonically oscillating the molten aluminum alloy to disperse and wet the graphitic particles in the alloy. 
     
     
         15 . The method of  claim 13 , further comprising injecting a gas into the molten metal to form microbubbles in the molten metal; and agglomerating the graphitic particles on or around the microbubbles to enhance the dispersion of the graphitic particles in the molten metal. 
     
     
         16 . The method of  claim 13 , wherein the graphitic particles comprise boron nitride. 
     
     
         17 . The method of  claim 13 , wherein the graphitic particles comprise one or more materials from the group consisting of boron nitride, graphite, tungsten disulfide and molybdenum disulfide. 
     
     
         18 . A method of making an aluminum alloy material, the method comprising:
 providing a molten aluminum alloy; adding graphitic particles to the molten aluminum alloy;   dispersing the graphitic particles in the molten aluminum alloy; and forming a molten aluminum master alloy.   
     
     
         19 . The method of  claim 18 , further comprising ultrasonically oscillating the molten aluminum alloy to disperse the graphitic particles in the master alloy. 
     
     
         20 . The method of  claim 18 , further comprising injecting a gas into the molten metal to form microbubbles in the molten metal; and agglomerating the graphitic particles around the microbubbles to enhance the dispersion of the graphitic particles in the molten master alloy. 
     
     
         21 . The method of  claim 18 , wherein the graphitic particles comprise boron nitride. 
     
     
         22 . The method of  claim 18 , wherein the graphitic particles comprise one or more materials from the group consisting of boron nitride, graphite, tungsten disulfide and molybdenum disulfide. 
     
     
         23 . The method of  claim 18 , wherein the graphitic particles comprise between 3.0% and 50%, by weight, of the master alloy.