Metal injection molding

Abstract

Feed material for use in producing a thixotropic alloy comprising pellets in the form of a solid cylinder having a length to diameter ratio in the range of from 1:1 to 2:1 and a maximum length of 0.250 inch.

Having thus described the invention, I claim:  
     
         1 . A method of producing feed material for use in producing a thixotropic alloy comprising introducing extrusion stock material of a metal alloy or composite into extruding apparatus, heating the stock material to an extrusion temperature therefor, extruding the stock material, and severing lengths of the extruded stock material to produce solid pellets of feed material having a maximum length to maximum thickness ratio of from about 0.8 to 4:1.  
     
     
         2 . The method according to  claim 1 , including the step of heating said pellets and shearing the pellets to produce a mixture of solid particles within a liquid matrix.  
     
     
         3 . The method according to  claim 2 , wherein said heating comprises heating said pellets in an extruder apparatus to a temperature above the solidus temperature, and wherein said shearing prevents the formation of large crystal structures in said mixture.  
     
     
         4 . The method according to  claim 3 , wherein said pellets are heated to a temperature below the liquidus temperature of the feed material.  
     
     
         5 . The method according to  claim 2 , wherein said heating comprises heating said pellets in a first zone in said extruder apparatus to a temperature above the liquidus temperature of said feed material to produce a substantially molten feed material, and cooling the substantially molten feed material in a second zone of said extruder apparatus to a temperature below the liquidus temperature but above the solidus temperature of the feed material.  
     
     
         6 . The method according to  claim 2 , wherein said heating and shearing includes the use of a screw extruder apparatus.  
     
     
         7 . The method according to  claim 5 , wherein said heating and shearing includes the use of a screw extruder apparatus includes the use of a screw extruder in said second zone to prevent the formation of large crystal structures in the molten feed material.  
     
     
         8 . The method according to  claim 2 , wherein said heating and shearing producing a mixture of solids and liquid, said mixture of solids and liquid being injected into a mold, and at least partially solidifying said mixture in the mold to produce an article, and removing the article from said mold.  
     
     
         9 . The method according to  claim 1 , wherein said ratio is about 1.1 to 2.5:1.  
     
     
         10 . The method according to  claim 1 , wherein the maximum thickness of the pellets of feed material is about 0.05 to 0.4 inch.  
     
     
         11 . The method according to  claim 1 , wherein the maximum length of the pellets is about 0.1 to 0.5 inch.  
     
     
         12 . The method according to  claim 1 , wherein said metal alloy or composite includes a metal selected from the group consisting of magnesium, magnesium alloy, or mixtures thereof.  
     
     
         13 . The method as defined in  claim 1 , wherein said pellets are substantially the same shape and size.  
     
     
         14 . The method as defined in  claim 1 , wherein said pellets include substantially cylindrically shaped pellets.  
     
     
         15 . The method as defined in  claim 1 , wherein said pellets include pellets having a substantially circular cross-sectional shape and a substantially triangular shaped side profile.  
     
     
         16 . The method as defined in  claim 1 , wherein said pellets include pellets having a substantially circular cross-sectional shape and a substantially trapezoidal side profile.  
     
     
         17 . The method as defined in  claim 1 , wherein said pellets include pellets having substantially a circular cross-sectional shape and a semi-trapezoidal side profile.  
     
     
         18 . A feed material of a metal alloy or metal composite for use in producing a thixotropic alloy, said feed material comprising solid cylindrical pellets having a length and a diameter, and a length to diameter ratio of from about 0.8:1 to 4:1.  
     
     
         19  The feed material according to  claim 18 , wherein said ratio is about 1:1 to 2.5:1.  
     
     
         20  The feed material according to  claim 18 , wherein said pellets have a maximum length of about 0.1 to 0.5 inch.  
     
     
         21 . The feed material according to  claim 18 , wherein the diameter of said pellets is about 0.05 to 0.4 inch.  
     
     
         22 . The feed material according to  claim 18 , wherein said metal alloy or metal composite includes a metal selected from the group consisting of magnesium, magnesium alloy, or mixtures thereof.  
     
     
         23 . The feed material according to  claim 18 , wherein said pellets include substantially cylindrically shaped pellets.  
     
     
         24 . The feed material according to  claim 18 , wherein said pellets include pellets having a substantially circular cross-sectional shape and a substantially triangular shaped side profile.  
     
     
         25 . The feed material according to  claim 18 , wherein said pellets include pellets having a substantially circular cross-sectional shape and a substantially trapezoidal side profile.  
     
     
         26 . The feed material according to  claim 18 , wherein said pellets have a substantially circular cross-sectional shape and a semi-trapezoidal side profile.  
     
     
         27 . A method of producing feed material for use in producing a thixotropic alloy from a plurality of pellets having a maximum length to maximum thickness ratio of from about 0.8 to 4:1, and heating said pellets and shearing the pellets to produce a mixture of solid particles within a liquid matrix.  
     
     
         28 . The method according to  claim 27 , wherein said heating comprises heating said pellets in screw extruder apparatus to a temperature above the solidus temperature but below the liquidus temperature of the feed material, and wherein said shearing comprises rotating this extruder screw to prevent the formation of large crystal structures in the mixture.  
     
     
         29 . The method according to  claim 27 , wherein said heating and shearing includes the use of a screw extruder apparatus.  
     
     
         30 . The method according to  claim 27 , wherein said heating comprises heating said pellets in a first zone in said extruder apparatus to a temperature above the liquidus temperature of said feed material to produce molten feed material, and cooling the molten feed material in a second zone of said extruder apparatus to a temperature below the liquidus temperature but above the solidus temperature of the feed material.  
     
     
         31 . The method according to  claim 30 , wherein said shearing comprises rotating the extruder screw in said second zone to prevent the formation of large crystal structures in the molten feed material.  
     
     
         32 . The method according to  claim 27 , wherein said pellets are substantially the same shape.  
     
     
         33 . The method according to  claim 27 , wherein said pellets are substantially the same size.