High Strength Microalloyed Magnesium Alloy

Abstract

A magnesium composite material and method for manufacturing a magnesium composite alloy wherein the magnesium composite alloy has improved thermal and mechanical properties. The improved thermal and mechanical properties are at least in part obtained by the modification of grain boundary properties in the magnesium composite alloy by the addition of nanoscale fillers to the magnesium composite alloy.

What is claimed: 
     
         1 . A magnesium composite alloy that includes:
 at least 60 wt. % magnesium;   more than 5 wt. % and less than 9 wt. % Rare Earth metal;   at least 0.5 wt. % zinc;   
       wherein said magnesium composite alloy has a thermal conductivity that is at least 170 W/m-K, and/or has a ductility exceeding 6% elongation to failure. 
     
     
         2 . A magnesium alloy composite comprising:
 at least 60 wt. % magnesium;   2.5-16 wt. % Rare Earth metal, said Rare Earth metal includes yttrium and/or gadolinium;   zinc, said zinc is less than 8 wt. %;   less than 1 wt. % zirconium;   up to 1 wt. % tin;   up to 1 wt. % germanium; and,   less than 10 wt. % aluminum; and   
       wherein said magnesium alloy composite includes an LPSO phase. 
     
     
         3 . A magnesium composite alloy that includes:
 at least 60 wt. % magnesium;   more than 5 wt. % and less than 9 wt. % Rare Earth metal;   at least 0.5 wt. % zinc;   
       wherein said magnesium alloy contains at least 10% LPSO phase; and, 
       wherein at least one additional precipitate in addition to the LPSO phase is present in an amount at least 1 vol. %; and, 
       wherein said magnesium composite alloy has an ultimate tensile strength of at least 240 MPa and/or has a ductility exceeding 6% elongation to failure. 
     
     
         4 . A magnesium alloy composite comprising:
 at least 60 wt. % magnesium;   2.5-16 wt. % Rare Earth metal, said Rare Earth metal includes yttrium and/or gadolinium;   zinc, said zinc is less than 8 wt. %; and,   
       wherein said magnesium alloy composite includes an LPSO phase. 
     
     
         5 . The magnesium composite alloy as defined in  claim 4 , wherein said magnesium composite alloy includes 0.5-3 wt. % zinc. 
     
     
         6 . The magnesium composite alloy as defined in  claim 4 , wherein said Rare Earth metal includes yttrium and non-yttrium rare earth metal, said non-yttrium includes gadolinium and/or neodymium, a weight ratio of non-yttrium rare earth metal to yttrium about 1:1 to 20:1. 
     
     
         7 . The magnesium composite alloy as defined in  claim 4 , wherein said Rare Earth metal includes 0.5-2 wt. % cerium and one or more other of said Rare Earth metals selected from the group consisting of gadolinium, neodymium, and/or yttrium. 
     
     
         8 . The magnesium composite alloy as defined in  claim 4 , wherein said Rare Earth metal includes up to 4 wt. % neodymium. 
     
     
         9 . The magnesium composite alloy as defined in  claim 4 , wherein said Rare Earth metal further including one or more of lanthanum, cerium, europium, and ytterbium. 
     
     
         10 . The magnesium composite alloy as defined in  claim 4 , wherein said Rare Earth metal includes more than 5 wt. % Rare Earth metal and less than 9 wt. % Rare Earth metal, said Rare Earth metal includes yttrium and non-yttrium rare earth metal, said Rare Earth metal includes 2-4 wt. % yttrium, at least 50% of said non-yttrium rare earth metal includes gadolinium, cerium, and/or neodymium, a weight ratio of non-yttrium to yttrium is 1:1 to 2.1. 
     
     
         11 . The magnesium composite alloy as defined in  claim 4 , wherein said magnesium composite alloy further includes a precipitate forming additive selected from calcium, aluminum, tin, zirconium, strontium, and manganese. 
     
     
         12 . The magnesium composite alloy as defined in  claim 4 , wherein said magnesium composite alloy further includes nickel and/or copper. 
     
     
         13 . The magnesium composite alloy as defined in  claim 4 , wherein a weight ratio of Rare Earth metal to zinc is 1.2-6:1. 
     
     
         14 . The magnesium composite alloy as defined in  claim 4 , wherein said magnesium composite alloy contains more than 0.5 wt. % zinc and less than 3 wt. % zinc. 
     
     
         15 . The magnesium composite alloy as defined in  claim 4 , wherein a total of said LPSO phases in said magnesium composite alloy constitutes 2-60 vol. % of said magnesium composite alloy. 
     
     
         16 . The magnesium composite alloy as defined in  claim 4 , wherein a total of said LPSO phases in said magnesium composite alloy constitutes 2-60 vol. % of said magnesium composite alloy, and said magnesium composite alloy includes at least 5 vol. % of one or more secondary phase precipitates. 
     
     
         17 . The magnesium composite alloy as defined in  claim 16 , wherein a total of said secondary precipitate phases in said magnesium composite alloy constitutes 5-30 vol. % of said magnesium composite alloy. 
     
     
         18 . The magnesium composite alloy as defined in  claim 16 , wherein said secondary precipitate phase includes magnesium—Rare Earth metals and/or precipitate that is absent Rare Earth metals. 
     
     
         19 . The magnesium composite alloy as defined in  claim 16 , wherein said LPSO phase and/or said secondary precipitate phase has a maximum dimension of less than 100 μm. 
     
     
         20 . The magnesium composite alloy as defined in  claim 4 , wherein said magnesium composite alloy has a tensile yield strength of greater than 280 MPa at 25° C., and/or an elongation to failure (Ef) of at least 6%. 
     
     
         21 . The magnesium composite alloy as defined in  claim 4 , wherein said magnesium composite alloy has a) a UTS of at least 400 MPa, b) a YS of at least 300 MPa, and/or c) an Ef of at least 6%. 
     
     
         22 . The magnesium composite alloy as defined in  claim 4 , wherein said magnesium composite alloy has a thermal conductivity greater than 175 W/m-K. 
     
     
         23 . The magnesium composite alloy as defined in  claim 4 , further including carbon, carbide, or oxide nanoparticles in an amount of 0.5-3 wt % 
     
     
         24 . A method for forming said magnesium composite alloy as defined in  claim 4 , wherein said magnesium composite alloy is direct chilled, sanded, and/or permanent mold cast, and then solutionized at 480-540° C. for at least 5 hours to partially or fully remove eutectic phases in said magnesium composite alloy. 
     
     
         25 . A method for forming said magnesium composite alloy as defined in  claim 4 , wherein said magnesium composite alloy is subject to an annealing precipitation/aging heat treatment for 4-50 hours at a temperature of 200-350° C. 
     
     
         26 . A method for forming said magnesium composite alloy as defined in  claim 4 , wherein said magnesium composite alloy is subject to a two-stage aging process wherein said LPSO phase is evolved continuously in said magnesium composite alloy at 300-400° C. for up to 24 hrs., and then heat treated at 200-300° C. for up to 48 hrs. to promote precipitation of said LPSO phase, a magnesium—Rare Earth metals phase, and/or a secondary precipitate phase. 
     
     
         27 . A method for forming said magnesium composite alloy as defined in  claim 4 , wherein said magnesium composite alloy is subject to a single stage heat treatment at 200-350° C. to co-precipitate said LPSO phase, and a magnesium—Rare Earth metals phase and/or a secondary precipitate phase.