Metal matrix composite having improved microstructure and the process for making the same

Abstract

The microstructure of a metal matrix composite comprising copper and reinforcement material is improved when the metal matrix composite comprises at least about 0.02% by weight of at least one of silver and gold. In one embodiment, the process for making a metal matrix composite comprises compacting powder particles of a reinforcement material to form a green compact, sintering the green compact to produce a porous skeletal body and infiltrating the porous skeletal body with an infiltrant comprising copper and at least about 0.1% of at least one of silver and gold, based on the weight of infiltrant. In another embodiment, the process comprises forming a mixture of particles of reinforcement material, copper and at least about 0.02% by weight of at least one of silver and gold, compacting the mixture to form a green compact, and sintering the green compact to form a near net shape metal matrix composite. The metal matrix composite has a more uniform microstructure along its cross-section and increased density, thereby providing for improved physical and thermal properties.

We claim:  
     
         1 . A process for making a metal matrix composites comprising: 
 compacting powder particles of reinforcement material to obtain a green compact;    sintering the green compact to obtain a porous skeletal body; and    infiltrating the porous skeletal body with an infiltrant comprising copper and at least about 0.1% of silver or gold, based on the weight of the infiltrant, to obtain a near net shape matrix metal composite.    
     
     
         2 . The process of  claim 1  wherein the infiltrant comprises at least about 0.1% of silver or gold based on the weight of the infiltrant.  
     
     
         3 . The process of  claim 1  wherein the infiltrant comprises silver and the silver is present in the form of a copper-silver alloy.  
     
     
         4 . The process of  claim 3  wherein the copper-silver alloy comprises from about 10% to about 40% by weight copper with the remainder being substantially silver.  
     
     
         5 . The process of  claim 3  wherein the copper-silver alloy is a copper-silver eutectic composition.  
     
     
         6 . The process of  claim 1  wherein: 
 the infiltrant comprises gold and the gold is present in the form of a copper-gold alloy.  
 
     
     
         7 . The process of  claim 6  wherein the copper-gold alloy comprises from about 10% to about 40% by weight copper with the remainder being substantially gold.  
     
     
         8 . The process of  claim 6  wherein the copper-gold alloy is a copper-gold eutectic composition.  
     
     
         9 . The process of  claim 1  wherein: 
 the infiltrant comprises at least about 0.3% silver present in the form of copper-silver alloy, based on the weight of infiltrant, with the remainder of the infiltrant being substantially copper.  
 
     
     
         10 . The process of  claim 1  wherein the reinforcement material has a melting temperature of at least about 1180° C.  
     
     
         11 . The process of  claim 1  wherein the reinforcement material is selected from the group consisting of tungsten, molybdenum, iron-nickel alloy, Invar®, iron-nickel-cobalt alloy, Kovar®, tantalum, chromium, osmium, ruthenium, rhenium, rhodium, hafnium, zirconium, nickel, iron, cobalt, titanium, titanium carbide, tungsten carbide, tantalum carbide, chromium carbide, silicon carbide, beryllium oxide, aluminum oxide, boron nitride, aluminum nitride, silicon nitride and mixtures thereof.  
     
     
         12 . The process of  claim 1  wherein the reinforcement material is at least one of tungsten and molybdenum.  
     
     
         13 . The process of  claim 1  wherein the particles of reinforcement material have a mean particle size ranging from about 2 microns to about 20 microns.  
     
     
         14 . The process of  claim 1  wherein the particles of reinforcement material are compacted to form green compact having a density that ranges from about 50% to about 95% of theoretical density.  
     
     
         15 . The process of  claim 1  wherein the green compact is sintered in a gas atmosphere comprising hydrogen and having a dew point of at least about 0° C.  
     
     
         16 . The process of  claim 15  wherein the green compact is sintered at a temperature ranging from about 1400° C. to about 1500° C. for about 0.5 hours to about 2 hours.  
     
     
         17 . The process of  claim 1  wherein the porous skeletal body produced upon sintering has a density ranging from about 50% to about 95% of theoretical density.  
     
     
         18 . The process of  claim 1  wherein the porous skeletal body is infiltrated in a gas atmosphere having a dew point of about 10° C. or less.  
     
     
         19 . The process of  claim 1  wherein the porous skeletal body is infiltrated at a temperature ranging from about 1100° C. to about 1500° C.  
     
     
         20 . The process of  claim 1  wherein the near net shape metal matrix composite comprises from about 5% to about 50% copper, from about 50% to about 95% reinforcement material, and at least about 0.05% by weight of silver.  
     
     
         21 . The process of  claim 1  wherein the powder particles of the reinforcement material are mixed with powder particles of copper before being compacted to form a green compact.  
     
     
         22 . The process of  claim 1  wherein the powder particles of the reinforcement material are mixed with powder particles of silver before being compacted to form a green compact prior to sintering the green compact.  
     
     
         23 . A process for making a matrix metal composites comprising: 
 compressing powder particles of a reinforcement material to obtain a green compact;    sintering the green compact to obtain a porous skeletal body; and    infiltrating the porous skeletal body with an infiltrant comprising copper and at least about 0.1% of silver or gold, based on the weight of the infiltrant, in the form of a copper-silver alloy, the silver being in form of a copper-silver alloy and the gold being in the form of a copper-gold alloy, to obtain a near net shape matrix metal composite.    
     
     
         24 . The process of  claim 23  wherein: 
 the reinforcement material is selected from the group consisting of tungsten, molybdenum, iron-nickel alloy, Invar®, iron-nickel-cobalt alloy, Kovar®, tantalum, chromium, osmium, ruthenium, rhenium, rhodium, hafnium, zirconium, nickel, iron, cobalt, titanium, titanium carbide, tungsten carbide, tantalum carbide, chromium carbide, silicon carbide, beryllium oxide, aluminum oxide, boron nitride, aluminum nitride and silicon nitride and mixtures thereof;  
 the infiltrant comprises at least about 0.1% copper-silver alloy, based on the weight of infiltrant, with the remainder of the infiltrant being copper; and  
 the copper-silver alloy comprises, by weight, from about 60% to about 90% silver with the remainder being substantially copper.  
 
     
     
         25 . The process of  claim 24  wherein the copper-silver alloy is the eutectic composition.  
     
     
         26 . The process of  claim 25  wherein the reinforcement material is tungsten or molybdenum.  
     
     
         27 . The process of  claim 23  wherein: 
 the reinforcement material is selected from the group consisting of tungsten, molybdenum, iron-nickel alloy, Invar®, iron-nickel-cobalt alloy, Kovar®, tantalum, chromium, osmium, ruthenium, rhenium, rhodium, hafnium, zirconium, nickel, iron, cobalt, titanium, titanium carbide, tungsten carbide, tantalum carbide, chromium carbide, silicon carbide, beryllium oxide, aluminum oxide, boron nitride, aluminum nitride, silicon nitride and mixtures thereof; and  
 the infiltrant comprises at least about 0.1% copper-gold alloy, based on the weight of infiltrant, with the remainder being copper; and  
 the copper-gold alloy comprises, by weight, from about 60% to about 90% gold with the remainder being substantially copper.  
 
     
     
         28 . The process of  claim 26  wherein the copper-gold alloy is the eutectic composition.  
     
     
         29 . The process of  claim 28  wherein the reinforcement material is tungsten or molybdenum.  
     
     
         30 . The process of  claim 23  wherein: 
 the green compact is sintered in a gas atmosphere comprising hydrogen and having a dew point of at least about 0° C. to produce a porous skeletal body having a density ranging from about 50% to about 95% of theoretical density.  
 
     
     
         31 . The process of  claim 23  wherein: 
 the porous skeletal body is infiltrated in a gas atmosphere having a dew point of about 10° C. or less.  
 
     
     
         32 . The process of  claim 31  wherein the porous skeletal body is infiltrated at a temperature ranging from about 1100° C. to about 1500° C.  
     
     
         33 . The process of  claim 31  wherein: 
 the infiltrant comprises at least about 0.1% silver in the form of copper-silver alloy, based on the weight of infiltrant, the copper-silver alloy comprising, by weight, from about 60% to about 90% silver and the remainder being substantially copper; and  
 the near net shape metal matrix composite comprises, by weight, from about 5% to about 50% copper, from about 50% to about 95% reinforcement material, and at least about 0.02% silver.  
 
     
     
         34 . The process of  claim 31  wherein: 
 the infiltrant comprises from about 0.3% to about 20% silver in the form of copper-silver alloy, based on the weight of infiltrant, the copper-silver alloy comprising, by weight, from about 60% to about 90% silver and the remainder being substantially copper; and  
 the near net shape metal matrix composite comprises, by weight, from about 10% to about 20% copper, from about 70% to about 90% reinforcement material, and from about 0.03% to about 10% silver; and  
 the reinforcement material is tungsten or molybdenum.  
 
     
     
         35 . A process for making a metal matrix composites comprising: 
 forming a mixture comprising, by weight, from about 5% to about 50% copper, from about 50% to about 95% reinforcement material, and at least about 0.02% of at least one of silver in the form of a copper-silver alloy or gold in the form of a copper-gold alloy, to form a mixture;    compressing the mixture to obtain a green compact; and    sintering the green compact to obtain a near net shape matrix metal composite.    
     
     
         36 . The process of  claim 35  wherein: 
 the mixture comprises from about 0.03% to about 10% by weight silver in the form of a copper-silver alloy composition, wherein copper-silver alloy composition comprises from about 10% to about 40% copper and from about 60% to about 90% silver;  
 the reinforcement material is selected from the group consisting of tungsten, molybdenum, iron-nickel alloy, Invar®, iron-nickel-cobalt alloy, Kovar®, tantalum, chromium, osmium, ruthenium, rhenium, rhodium, hafiium, zirconium, nickel, iron, cobalt, titanium, titanium carbide, tungsten carbide, tantalum carbide, chromium carbide, silicon carbide, beryllium oxide, aluminum oxide, boron nitride, aluminum nitride, silicon nitride and mixtures thereof; and  
 the green compact is sintered in a gas atmosphere comprising hydrogen and having a dew point of at least about 0° C.  
 
     
     
         37 . The process of  claim 35  wherein: 
 the mixture comprises from about 0.03% to about 10% by weight gold in the form of a copper-gold alloy composition, wherein the copper-gold alloy composition comprises from about 10% to about 40% copper and from about 90% to about 60% gold;  
 the reinforcement material is selected from the group consisting of tungsten, molybdenum, iron-nickel alloy, Invar®, iron-nickel-cobalt alloy, Kovar®, tantalum, chromium, osmium, ruthenium, rhenium, rhodium, hafnium, zirconium, nickel, iron, cobalt, titanium, titanium carbide, tungsten carbide, tantalum carbide, chromium carbide, silicon carbide, beryllium oxide, aluminum oxide, boron nitride, aluminum nitride, silicon nitride and mixtures thereof; and  
 the green compact is sintered in a gas atmosphere comprising hydrogen and having a dew point of at least about 0° C.  
 
     
     
         38 . A metal matrix composite comprising, by weight: 
 at least about 0.03% silver or gold;    from about 5% to about 50% copper; and    from about 50% to about 95% reinforcement material.    
     
     
         39 . The metal matrix composite of  claim 38  wherein the metal matrix composite comprises from about 0.03% to about 10% by weight silver.  
     
     
         40 . The metal matrix composite of  claim 38  wherein the metal matrix composite comprises from about 0.03% to about 10% by weight gold.  
     
     
         41 . The metal matrix composite of  claim 38  wherein the reinforcement material has a melting point of at least about 100° C. greater than the melting point of copper.  
     
     
         42 . The metal matrix composite of  claim 38  wherein the reinforcement material is selected from the group consisting of: 
 tungsten, molybdenum, iron-nickel alloy, Invar®, iron-nickel-cobalt alloy, Kovar®, tantalum, chromium, osmium, ruthenium, rhenium, rhodium, hafnium, zirconium, nickel, iron, cobalt, titanium, titanium carbide, tungsten carbide, tantalum carbide, chromium carbide, silicon carbide, beryllium oxide, aluminum oxide, boron nitride, aluminum nitride, silicon nitride and mixtures thereof.  
 
     
     
         43 . The metal matrix composite of  claim 38  wherein the metal matrix composite comprises from about 0.05% to about 5% by weight silver.  
     
     
         44 . The metal matrix composite of  claim 38  wherein the metal matrix composite comprises from about 0.05% to about 5% by weight gold.  
     
     
         45 . The metal matrix composite of  claim 38  wherein the metal matrix composite comprises by weight: 
 from about 0.05% to about 5% silver;  
 from about 10% to about 30% copper; and  
 from about 70% to about 90% reinforcement material.  
 
     
     
         46 . The metal matrix composite of  claim 38  wherein the metal matrix composite comprises by weight: 
 from about 0.05% to about 5% gold;  
 from about 10% to about 30% copper; and  
 from about 70% to about 90% reinforcement material.  
 
     
     
         47 . The metal matrix composite of  claim 45  wherein the reinforcement material comprises at least one of tungsten and molybdenum.  
     
     
         48 . The metal matrix composite of  claim 46  wherein the reinf orcement material comprises at least one of tungsten and molybdenum.  
     
     
         49 . The metal matrix composite of  claim 45  further comprising gold.  
     
     
         50 . The metal matrix composite of  claim 46  further comprising silver.