High Conductivity Magnesium Alloy

Abstract

A castable, moldable, or extrudable magnesium-based alloy that includes one or more insoluble additives. The insoluble additives can be used to enhance the mechanical properties of the structure, such as ductility and/or tensile strength. The final structure can be enhanced by heat treatment, as well as deformation processing such as extrusion, forging, or rolling, to further improve the strength of the final structure as compared to the non-enhanced structure. The magnesium-based composite has improved thermal and mechanical properties by the modification of grain boundary properties through the addition of insoluble nanoparticles to the magnesium alloys. The magnesium-based composite can have a thermal conductivity that is greater than 180 W/m−K, and/or ductility exceeding 15-20% elongation to failure.

What is claimed: 
     
         1 . A magnesium-based composite comprising a base metal and a plurality of insoluble nanoparticles, said base metal formed of a magnesium or magnesium alloy, said base metal including at least 70 wt. % magnesium, said insoluble nanoparticles having a melting point that is greater than a melting point of said base metal, said insoluble nanoparticles having a solubility of less than about 5% in said base metal, said insoluble nanoparticles constituting at least 0.1 vol. % of said magnesium-based composite, at least 50% of said insoluble nanoparticles located within 200 nm of grain boundaries or dislocations in said magnesium-based composite, said insoluble nanoparticles having an average thermal conductivity of above about 140 W/m−K, said magnesium-base composite having at least one property that is at least 10% greater than a same property of said base metal that is absent said insoluble nanoparticles, said property selected from the group consisting of thermal conductivity, strength, modulus and ductility. 
     
     
         2 . The magnesium-based composite as defined in  claim 1 , wherein a weight percent of said base metal is greater than a weight percent of said insoluble nanoparticles. 
     
     
         3 . The magnesium-based composite as defined in  claim 1 , wherein said insoluble nanoparticles constitute about 0.1-20 vol. % of said magnesium-based composite. 
     
     
         4 . The magnesium-based composite as defined in  claim 1 , wherein at least 50% of said insoluble nanoparticles have an average particle size or have at least one dimension that is no more than about 400 nm. 
     
     
         5 . The magnesium-based composite as defined in  claim 1 , wherein said base metal is a magnesium alloy selected from the group consisting of AM series alloy, AZ series alloy, LPSO series alloy, WE series alloy, ZE series alloy, ZK series alloy, ZM5 series alloy, or ZW series alloy. 
     
     
         6 . The magnesium-based composite as defined in  claim 1 , wherein said magnesium-based composite has ultimate tensile strength of greater than 30 ksi. 
     
     
         7 . The magnesium-based composite as defined in  claim 1 , wherein said magnesium-based composite has been subjected to semi-solid processing, such as thixomolding, thixocasting, continuous reheocasting, or strain-induced melt activation (SIMA) processing to improve ductility of said magnesium-based composite. 
     
     
         8 . The magnesium-based composite as defined in  claim 1 , wherein said nanoparticles are selected from the group consisting of fullerenes, multi-walled nanotubes, single-walled nanotubes, graphene, nanodiamonds, buckeyballs, platelets, flakes, powder, nanowires, chopped fibers, and intermetallics particles. 
     
     
         9 . The magnesium-based composite as defined in  claim 1 , wherein said nanoparticles are included on inert ceramic. 
     
     
         10 . The magnesium-based composite as defined in  claim 9 , wherein said nanoparticles included in inert ceramic include material are selected from the group consisting of W, SiC, AlN, BeO, BN, and TiB 2 , and high thermal conductivity MAX phase materials. 
     
     
         11 . The magnesium-based composite as defined in  claim 8 , wherein said intermetallic particles including one or more high thermal conductivity materials are selected from the group consisting of Cu, Ag, Al, Be, Au, and compounds and alloys thereof. 
     
     
         12 . The magnesium-based composite as defined in  claim 1 , further including insoluble micron-size particles, said insoluble micron-sized particles having a solubility of less than about 5% in said base metal. 
     
     
         13 . The magnesium-based composite as defined in  claim 12 , wherein said insoluble micron-size particles have an average thermal conductivity of greater than about 140 W/m−K. 
     
     
         14 . The magnesium-based composite as defined in  claim 12 , wherein said insoluble micron-size particles include one or more materials selected from the group consisting of diamond, heat treated carbon fiber, SiC particles, fibers, whiskers, heat-treated graphite, AlN, BN, and other high thermal conductivity, thermally stable materials. 
     
     
         15 . The magnesium-based composite as defined in  claim 12 , wherein said insoluble micron-size particles constitute about 0.1-49.5 vol. % of said magnesium-based composite. 
     
     
         16 . The magnesium-based composite as defined in  claim 1 , wherein said magnesium-based composite has a dissolution rate in tap water or brine of about 10-200 Mg/cm 2 /hr. at a temperature of at least about 55° C. 
     
     
         17 . The magnesium-based composite as defined in  claim 1 , wherein said magnesium-based composite includes one or more metals selected from the group consisting of a) 0.1-10 wt. % aluminum, b) 0.1-9 wt. % calcium, c) 0.1-3 wt. % strontium, d) 0.1-6 wt. % zinc, e) 0.1-1 wt. % zirconium, f) 0.1-5 wt. % niobium, g) 0.1-10 wt. % lithium, h) 0.1-8 wt. % tin, i) 0.1-10 wt. % lanthanide elements, and j) 0.1-10 wt. % yttrium. 
     
     
         18 . The magnesium-based composite as defined in  claim 1 , wherein said insoluble nanoparticles include first and second particles, said first particles having a different composition than said second particles. 
     
     
         19 . A method for forming a magnesium-based composite comprising:
 providing a base metal formed of a magnesium or magnesium alloy, said base metal including at least 70 wt. % magnesium;   providing a plurality of insoluble nanoparticles having a melting point that is greater than a melting point of said base metal, said insoluble nanoparticles having a solubility of less than about 5% in said base metal, said insoluble nanoparticles having an average thermal conductivity of above about 140 W/m−K;   heating said base metal until molten;   mixing said plurality of insoluble nanoparticles in said molten base metal to form a mixture and to cause said plurality of particles to disperse in said mixture; and,   cooling said mixture to form said magnesium-based composite;   wherein said plurality of insoluble nanoparticles are disbursed in said magnesium-based composite, at least 50% of said insoluble nanoparticles are located within 200 nm of grain boundaries or dislocations in said magnesium-based composite, said insoluble nanoparticles constituting at least 0.1 vol. % of said magnesium-based composite, said magnesium-base composite having at least one property that is at least 10% greater than a same property of said base metal that is absent said insoluble nanoparticles, said property selected from the group consisting of thermal conductivity, strength, modulus, and ductility.   
     
     
         20 . The method as defined in  claim 19 , wherein said step of mixing includes mixing using one or more processes selected from the group consisting of thixomolding, stir casting, mechanical agitation, electrowetting, and ultrasonic dispersion. 
     
     
         21 . The method as defined in  claim 19 , including the further step of heat treating said magnesium-based composite to improve tensile strength, elongation, or combinations thereof without significantly affecting a dissolution rate of said magnesium-based composite. 
     
     
         22 . The method as defined in  claim 19 , including the further step of forming said magnesium-based composite into a device for: a) separating hydraulic fracturing systems and zones for oil and gas drilling; b) structural support or component isolation in oil and gas drilling and completion systems; or c) combinations thereof.