Magnesium-based alloy for semi-solid casting having elevated temperature properties

Abstract

A magnesium-based semi-solid alloy having improved creep resistance, ultimate tensile strength, tensile yield strength and average % elongation at 150° C. Castings are cast from a semi-solid alloy slurry comprising, in weight percent, between about 3 to 7% Aluminum, between about 0.5% and 3% Strontium with the balance being magnesium except for impurities commonly found in magnesium alloys. The semi-solid alloy slurry includes up to 5% or up to about 20% solid fraction by weight.

1 . A magnesium-based, semi-solid casting alloy having improved elevated temperature performance when cast from a semi-solid alloy slurry, the alloy comprising, in weight percent, from about 3 to 7% aluminum, from about 0.5 to 3% strontium, with the balance being magnesium, except for impurities commonly found in magnesium alloys, wherein, the semi-solid alloy slurry includes up to about 20% of a solid fraction by weight.  
     
     
         2 . The magnesium-based, semi-solid casting alloy of  claim 1 , wherein the alloy comprises 4.5 to 5.5% aluminum.  
     
     
         3 . The magnesium-based, semi-solid casting alloy of  claim 1 , wherein the alloy comprises from 1.2 to 2.2% strontium.  
     
     
         4 . The magnesium-based, semi-solid casting alloy of  claim 2 , wherein the alloy comprises from 1.2 to 2.2% strontium.  
     
     
         5 . The magnesium-based, semi-solid casting alloy of  claim 1 , wherein when cast, the casting has an average % creep deformation at 150° C. of less than or equal to about 0.04%, an average ultimate tensile strength at 150° C. of at least about 174 MPa, an average tensile yield strength at 150° C. of at least about 112 MPa, and an average % elongation at 150° C. of less than or equal to about 20%.  
     
     
         6 . The magnesium-based, semi-solid casting alloy of  claim 5 , wherein when cast, the casting has an average % creep deformation at 150° C. of about 0.04%, an average ultimate tensile strength at 150° C. of about 174 MPa, an average tensile yield strength at 150° C. of about 112 MPa, and an average % elongation at 150° C. of about 20%.  
     
     
         7 . A magnesium-based, semi-solid casting alloy having improved elevated temperature performance when cast from a semi-solid alloy slurry, the alloy comprising, in weight percent, from about 3 to 7% aluminum, from about 0.5 to 3% strontium, with the balance being magnesium, except for impurities commonly found in magnesium alloys, wherein, the semi-solid alloy slurry includes up to about 5% of a solid fraction by weight.  
     
     
         8 . The magnesium-based, semi-solid casting alloy of  claim 7 , wherein the alloy comprises from 4.5 to 5.5% aluminum.  
     
     
         9 . The magnesium-based, semi-solid casting alloy of  claim 7 , wherein the alloy comprises from 1.2 to 2.2% strontium.  
     
     
         10 . The magnesium-based, semi-solid casting alloy of  claim 8 , wherein the alloy comprises from 1.2 to 2.2% strontium.  
     
     
         11 . The magnesium-based, semi-solid casting alloy of  claim 7 , wherein when cast, the casting has an average % creep deformation at 150° C. of less than or equal to about 0.04%, an average ultimate tensile strength at 150° C. of at least about 183 MPa, an average tensile yield strength at 150° C. of at least about 116 MPa, and an average % elongation at 150° C. of less than or equal to at least about 17%.  
     
     
         12 . The magnesium-based, semi-solid casting alloy of  claim 11 , wherein when cast, the casting has an average % creep deformation at 150° C. of about 0.04%, an average ultimate tensile strength at 150° C. of about 183 MPa, an average tensile yield strength at 150° C. of about 116 MPa, and an average % elongation at 150° C. of about 17%.  
     
     
         13 . The magnesium-based, semi-solid casting alloy of  claim 1 , wherein the casting is cast using a thixotropic casting process.  
     
     
         14 . The magnesium-based, semi-solid casting alloy of  claim 7 , wherein the casting is cast using a thixotropic casting process.  
     
     
         15 . The magnesium-based, semi-solid casting alloy of  claim 1 , wherein the alloy has a structure including primary magnesium particles having a mean size of from about 20 to about 150 μm in a matrix of grains of magnesium having a mean size of from about 5 μm to about 20 μm reinforced with Al 4 Sr intermetallic homogeneously dispersed particles having a mean size of from about 1 μm to about 10 μm.  
     
     
         16 . The magnesium-based, semi-solid casting alloy of  claim 7 , wherein the alloy has a structure including primary magnesium particles having a mean size of from about 20 to about 150 μm in a matrix of grains of magnesium having a mean size of from about 5 μm to about 20 μm reinforced with Al 4 Sr intermetallic homogeneously dispersed particles having a mean size of from about 1 μm to about 10 μm.  
     
     
         17 . A magnesium-based casting having improved elevated temperature performance when cast from a semi-solid alloy slurry, the slurry comprising, in weight percent, from about 3 to 7% aluminum, from about 0.5 to 3% strontium, with the balance being magnesium, except for impurities commonly found in magnesium alloys, wherein, the semi-solid alloy slurry includes up to about 20% of a solid fraction by weight.  
     
     
         18 . The magnesium-based casting of  claim 17 , wherein the casting comprises from 4.5 to 5.5% aluminum.  
     
     
         19 . The magnesium-based casting of  claim 17 , wherein the alloy comprises from 1.2 to 2.2% strontium.  
     
     
         20 . The magnesium-based casting of  claim 18 , wherein the alloy comprises from 1.2 to 2.2% strontium.  
     
     
         21 . The magnesium-based casting of  claim 17 , wherein the casting has an average % creep deformation at 150° C. of less than or equal to about 0.04%, an average ultimate tensile strength at 150° C. of at least about 174 MPa, an average tensile yield strength at 150° C. of at least about 112 MPa, and an average % elongation at 150° C. of less than or equal to about 20%.  
     
     
         22 . The magnesium-based casting of  claim 21 , wherein the casting has an average % creep deformation at 150° C. of about 0.04%, an average ultimate tensile strength at 150° C. of about 174 MPa, an average tensile yield strength at 150° C. of about 112 MPa, and an average % elongation at 150° C. of about 20%.  
     
     
         23 . A magnesium-based casting having improved elevated temperature performance when cast from a semi-solid alloy slurry, the slurry comprising, in weight percent, from about 3 to 7% aluminum, from about 0.5 to 3% strontium, with the balance being magnesium, except for impurities commonly found in magnesium alloys, wherein, the semi-solid alloy slurry includes up to about 5% of a solid fraction by weight.  
     
     
         24 . The magnesium-based casting of  claim 23 , wherein the casting comprises from 4.5 to 5.5% aluminum.  
     
     
         25 . The magnesium-based casting of  claim 23 , wherein the casting comprises from 1.2 to 2.2% strontium.  
     
     
         26 . The magnesium-based casting of  claim 24 , wherein the casting comprises from 1.2 to 2.2% strontium.  
     
     
         27 . The magnesium-based casting of  claim 23 , wherein when cast, the casting has an average % creep deformation at 150° C. of less than or equal to about 0.04%, an average ultimate tensile strength at 150° C. of at least about 183 MPa, an average tensile yield strength at 150° C. of at least about 116 MPa, and an average % elongation at 150° C. of less than or equal to about 17%.  
     
     
         28 . The magnesium-based casting of  claim 27 , wherein when cast, the casting has an average % creep deformation at 150° C. of about 0.04%, an average ultimate tensile strength at 150° C. of about 183 MPa, an average tensile yield strength at 150° C. of about 116 MPa, and an average % elongation at 150° C. of about 17%.  
     
     
         29 . The magnesium-based casting of  claim 17 , wherein the casting is cast using a thixotropic casting process.  
     
     
         30 . The magnesium-based casting of  claim 23 , wherein the casting is cast using a thixotropic casting process.  
     
     
         31 . The magnesium-based semi-solid casting of  claim 17 , wherein said alloy has a structure including primary magnesium particles having a mean size of from about 20 to about 150 μm in a matrix of grains of magnesium having a mean size of from about 5 μm to about 20 μm reinforced with Al 4 Sr intermetallic homogeneously dispersed particles having a mean size of from about 1 μm to about 10 μm.  
     
     
         32 . The magnesium-based semi-solid casting of  claim 23 , wherein said alloy has a structure including primary magnesium particles having a mean size of from about 20 to about 150 μm in a matrix of grains of magnesium having a mean size of from about 5 μm to about 20>m reinforced with Al 4 Sr intermetallic homogeneously dispersed particles having a mean size of from about 1 μm to about 10 μm.