Discontinuous carbon fiber reinforced metal matrix composite

Abstract

Disclosed are methods and materials for preparing metal matrix composite (MMC) components that have low weight, good thermal conductivity and a controllable in-plane coefficient of thermal expansion. One embodiment of the invention features a metal matrix composite that includes a metal alloy and random in-plane discontinuous fibers. In some embodiments, the metal alloy includes aluminum, copper or magnesium. In certain embodiments, the metal matrix composite includes additives that enable solution hardening. In other embodiments, the metal matrix composite includes additives that enable precipitation hardening. Another embodiment of the invention features a method of manufacturing a metal matrix composite. The method includes contacting random in-plane discontinuous fibers with a binder, and pressurizing the random in-plane discontinuous fibers and the binder to form a bound preform. The preform is pressurized to a pressure greater than the molten metal capillary breakthrough pressure of the bound preform. Subsequently, the bound preform is placed in a mold, infiltrated with a molten infiltrant, and the molten infiltrant is cooled to form the metal matrix composite.

What is claimed is:  
     
         1 . A metal matrix composite comprising: 
 a metal alloy; and    random in-plane discontinuous fibers, wherein the random in-plane discontinuous fibers comprise carbon.    
     
     
         2 . The metal matrix composite of  claim 1  wherein the metal alloy comprises a major component selected from the group consisting of aluminum, copper, and magnesium.  
     
     
         3 . The metal matrix composite of  claim 1  wherein a majority of the random in-plane discontinuous fibers have a length less than approximately 750 μm.  
     
     
         4 . The metal matrix composite of  claim 1  wherein the random in-plane discontinuous fibers comprise graphite.  
     
     
         5 . The metal matrix composite of  claim 1  wherein the random in-plane discontinuous fibers are milled.  
     
     
         6 . The metal matrix composite of  claim 1  wherein the metal matrix composite has a volume fraction of the random in-plane discontinuous fibers in a range of approximately 0.15 to approximately 0.6.  
     
     
         7 . The metal matrix composite of  claim 1  wherein a minority of the random in-plane discontinuous fibers are oriented out of plane by an angle greater than 10°.  
     
     
         8 . The metal matrix composite of  claim 7  wherein less than 20% of the random in-plane discontinuous fibers are oriented out of plane by an angle greater than 10°.  
     
     
         9 . The metal matrix composite of  claim 1  wherein an in-plane coefficient of thermal expansion is in a range of approximately 3 ppm/°K to approximately 12 ppm/°K.  
     
     
         10 . The metal matrix composite of  claim 1  wherein an in-plane coefficient of thermal expansion is greater than the coefficient of thermal expansion of silicon.  
     
     
         11 . The metal matrix composite of  claim 2  wherein the major component of the metal alloy is aluminum, and the metal alloy further comprises more than approximately 4 wt % silicon.  
     
     
         12 . The metal matrix composite of  claim 11  wherein the silicon composition is approximately the eutectic composition.  
     
     
         13 . The metal matrix composite of  claim 1  wherein the random in-plane discontinuous fibers are uniformly distributed within the metal matrix composite.  
     
     
         14 . The metal matrix composite of  claim 11  wherein the metal alloy further comprises a minor component that enables precipitation hardening.  
     
     
         15 . The metal matrix composite of  claim 14  wherein the minor component is less than approximately 2 wt % magnesium.  
     
     
         16 . The metal matrix composite of  claim 2  wherein the major component of the metal alloy is copper, and the metal alloy further comprises less than approximately 5 wt % chromium.  
     
     
         17 . The metal matrix composite of  claim 16  wherein the metal alloy further comprises a minor component that enables solution hardening.  
     
     
         18 . The metal matrix composite of  claim 17  wherein the minor component is at less than approximately 2 wt % zirconium.  
     
     
         19 . The metal matrix composite of  claim 18  further comprising a nickel plating.  
     
     
         20 . An article of manufacture comprising the metal matrix composite of  claim 1 .  
     
     
         21 . A metal matrix composite comprising: 
 a metal alloy; and    random in-plane discontinuous fibers, wherein the random in-plane discontinuous fibers comprise carbon and are uniformly distributed within the metal matrix composite, and    wherein the metal matrix composite has a volume fraction of the random in-plane discontinuous fibers in a range of approximately 0.15 to approximately 0.6.    
     
     
         22 . A metal matrix composite comprising: 
 a metal alloy consisting essentially of aluminum, silicon and magnesium, wherein 
 the silicon is approximately 5 wt % to approximately 20 wt % of the metal alloy, and  
 the magnesium is approximately 0.1 wt % to approximately 2 wt % of the metal alloy; and  
   random in-plane discontinuous graphite fibers uniformly distributed within the metal matrix composite.    
     
     
         23 . A metal matrix composite comprising: 
 a metal alloy consisting essentially of copper, chromium and zirconium, wherein 
 the chromium is approximately 0.3 wt % to approximately 2 wt % of the metal alloy, and  
 the zirconium is approximately 0.1 wt % to approximately 1 wt % of the metal alloy; and  
   random in-plane discontinuous graphite fibers uniformly distributed in the metal matrix composite.    
     
     
         24 . A method of manufacturing a metal matrix composite, the method comprising the steps of: 
 contacting random in-plane discontinuous fibers with a binder;    pressurizing the random in-plane discontinuous fibers and the binder to form a bound preform, wherein the random in-plane discontinuous fibers and the binder are pressurized to a pressure greater than the capillary breakthrough pressure of the bound preform;    placing the bound preform in a mold;    infiltrating the bound preform with a molten infiltrant under a pressure at least equal to the capillary breakthrough pressure; and    cooling the molten infiltrant to form the metal matrix composite.    
     
     
         25 . The method of  claim 24  further comprising the steps of: 
 placing a second bound preform adjacent to the bound preform in the mold prior to the step of infiltrating;  
 contacting a surface of the bound preform with a surface of the second bound preform; and  
 removing the binder prior to the step of infiltrating to merge the surface of the bound preform with the surface of the second bound preform.  
 
     
     
         26 . The method of  claim 24  further comprising the steps of: 
 heating the bound preform in the mold;  
 evacuating the bound preform in the mold to create a reduced pressure within the bound preform; and  
 transporting a charge of the molten infiltrant into the mold while maintaining the reduced pressure within the preform.  
 
     
     
         27 . The method of  claim 24  further comprising the step of: 
 forming a preform of random in-plane discontinuous fibers,  
 wherein the step of forming the preform comprises agitating discontinuous fibers to promote a random in-plane orientation.  
 
     
     
         28 . The method of  claim 24  wherein the binder comprises a particulate, and the method further comprises the steps of: 
 liquefying the binder; and  
 solidifying the binder to form the bound preform.  
 
     
     
         29 . The method of  claim 24  wherein the random in-plane discontinuous fibers comprise carbon.