Light weight high stiffness metal composite

Abstract

Metal matrix composites are disclosed that have a low coefficient of thermal expansion and low density. The composite includes a matrix formed from a low CTE metal alloy in which micron-scale ceramic particles are homogeneously dispersed therein. Methods for producing such composites are also disclosed. The composites also have improved yield strength and specific modulus.

1 . A metal matrix composite, comprising:
 a matrix formed from a metal alloy that has a low coefficient of thermal expansion (CTE); and micron-scale ceramic particles dispersed in the matrix.   
     
     
         2 . The metal matrix composite of  claim 1 , wherein the metal alloy is selected from the group consisting of iron-nickel alloys and iron-nickel-cobalt alloys. 
     
     
         3 . The metal matrix composite of  claim 2 , wherein the metal alloy is an iron-nickel alloy containing from about 75 weight percent to about 55 weight percent iron and from about 25 weight percent to about 45 weight percent nickel. 
     
     
         4 . The metal matrix composite of  claim 1 , wherein the metal alloy has a coefficient of thermal expansion of less than 2 ppm/° K over a range of −60° C. to +60° C. 
     
     
         5 . The metal matrix composite of  claim 1 , wherein the ceramic particles are made from a material selected from the group consisting of nitrides, carbides, oxides, silicides, borides, and mixtures thereof. 
     
     
         6 . The metal matrix composite of  claim 5 , wherein the ceramic particles are nitrides selected from the group consisting of Si 3 N 4 , AlN, CrN, HfN, NbN, TaN, TiN, VN, and ZrN; or
 wherein the ceramic particles are carbides selected from the group consisting of Cr 3 C 2 , HfC, Mo 2 C, NbC, SiC, TaC, TiC, VC, WC, and ZrC; or   wherein the ceramic particles are oxides selected from the group consisting of Al 2 O 3 , HfO 2 , SiO 2 , Ta 2 O 5 , TiO 2 , Y 2 O 3 , ZrO 2 , and ZrSiO 4 .   
     
     
         7 . The metal matrix composite of  claim 1 , wherein the ceramic particles comprise from about 10 vol % to about 45 vol % of the metal matrix composite. 
     
     
         8 . The metal matrix composite of  claim 1 , wherein the ceramic particles have an average particle size of 1 micron to about 30 microns. 
     
     
         9 . The metal matrix composite of  claim 1 , wherein the metal matrix composite has a density of less than 7.5 g/cc. 
     
     
         10 . The metal matrix composite of  claim 1 , wherein the metal matrix composite has a coefficient of thermal expansion of from about 0.5 ppm/° K to about 1.0 ppm/° K over a range of −60° C. to +60° C. 
     
     
         11 . The metal matrix composite of  claim 1 , wherein the metal matrix composite has a specific modulus of 20 GPa/g/cc to 32 GPa/g/cc; or
 wherein the metal matrix composite has a 0.2% offset yield strength of 250 MPa to 600MPa according to EN6892/1: 2009 or ASTM E8M; or   wherein the metal matrix composite has a ductility of at least 2% when measured according to EN6892/1: 2009 or ASTM E8M.   
     
     
         12 . A method for producing a metal matrix composite, the method comprising the steps of:
 mixing (i) a metal alloy powder that has a low coefficient of thermal expansion (CTE) with (ii) micron-scale ceramic particles to form a mixture;   mechanically alloying the mixture;   hot isostatic pressing the mixture to obtain a billet;   forging the billet to obtain the metal matrix composite.   
     
     
         13 . The method of  claim 12 , wherein the mechanical alloying results in an even distribution of the ceramic particles in a metallic matrix formed from the metal alloy powder. 
     
     
         14 . The method of  claim 12 , wherein the mechanical alloying is performed by milling. 
     
     
         15 . The method of  claim 12 , wherein the hot isostatic pressing is performed at a temperature of about 1000° C. to about 1200° C. and a pressure of about 30 MPa to about 150 MPa for a period of about 1 hour to about 8 hours. 
     
     
         16 . The method of  claim 12 , wherein the forging is performed at a temperature of about 1000° C. to about 1200° C. 
     
     
         17 . The metal matrix composite produced by the method of  claim 12 . 
     
     
         18 . A composition comprising a metal matrix composite, wherein the metal matrix composite includes (a) a matrix formed from a metal alloy that has a low coefficient of thermal expansion (CTE); and (b) micron-scale ceramic particles homogeneously dispersed in the matrix. 
     
     
         19 . An article formed from a metal matrix composite, wherein the metal matrix composite includes (a) a matrix formed from a metal alloy that has a low coefficient of thermal expansion (CTE); and (b) micron-scale ceramic particles dispersed in the matrix. 
     
     
         20 . The article of  claim 19 , wherein the article is used in aerospace, space, electronics and defense applications, or in electronics packaging.