Process for casting a semi-solid metal alloy

Abstract

A method of forming a metal part includes heating a metal alloy composition to form a liquid that is substantially free of metal solids. The liquid is cooled to form a semi-solid metal alloy slurry having a low weight percentage of substantially non-dendritic solids. The semi-solid metal alloy slurry is transferred to a mold at a low pressure and is cooled to cast a substantially solid part.

1 . A method of forming a metal part, comprising: 
 heating a metal alloy composition to form a liquid that is substantially free of metal solids;    cooling the liquid to form a semi-solid metal alloy slurry having a weight percentage of solids in the range of about one percent to about thirty percent and being substantially free of dendritic solids;    transferring the semi-solid metal alloy slurry to a mold;    cooling the semi-solid metal alloy slurry in the mold at a pressure of about one hundred pounds per square inch or less to cast a substantially solid part.    
   
   
       2 . The method of  claim 1 , wherein: 
 the semi-solid metal alloy slurry is cast at a pressure of about fifteen pounds per square inch or less.    
   
   
       3 . The method of  claim 1 , wherein: 
 the semi-solid metal alloy slurry is cast at atmospheric pressure.    
   
   
       4 . The method of  claim 1 , wherein: 
 the substantially solid part is cast utilizing a sand casting process.    
   
   
       5 . The method of  claim 1 , wherein: 
 the substantially solid part is cast utilizing a lost foam casting process.    
   
   
       6 . The method of  claim 1 , wherein: 
 the semi-solid metal alloy slurry has a weight percentage of solids of about one percent to about twenty percent.    
   
   
       7 . The method of  claim 1 , wherein: 
 the semi-solid metal alloy slurry has a weight percentage of solids of about five percent to about ten percent.    
   
   
       8 . The method of  claim 1 , wherein: 
 the solids in the semi-solid metal alloy slurry comprise substantially spheroidal particles.    
   
   
       9 . The method of  claim 1 , wherein: 
 the metal alloy comprises aluminum.    
   
   
       10 . The method of  claim 1 , wherein: 
 the metal alloy comprises a titanium alloy.    
   
   
       11 . A method of casting metallic parts, comprising: 
 forming a semi-solid metal alloy slurry having a weight percentage of solids of about thirty percent or less, the semi-solid metal alloy slurry being substantially free of dendritic solids;    transferring the semi-solid metal alloy slurry to a mold having a mold cavity, such that the semi-solid metal alloy slurry flows into the mold cavity;    cooling the semi-solid metal alloy slurry in the mold cavity to substantially solidify the semi-solid metal alloy slurry and form a part;    pressurizing the semi-solid metal alloy slurry in the mold cavity at a low pressure as the metal alloy is cooled.    
   
   
       12 . The method of  claim 11 , wherein: 
 the semi-solid metal alloy slurry is cast at a pressure of about one hundred pounds per square inch or less.    
   
   
       13 . The method of  claim 11 , wherein: 
 the semi-solid metal alloy slurry comprises globular solids.    
   
   
       14 . The method of  claim 11 , wherein: 
 the mold further comprises a sprue and runner in fluid communication with the mold cavity and an upwardly opening pouring basin connected to the sprue; and    the semi-solid metal alloy slurry is poured into the pouring basin.    
   
   
       15 . The method of  claim 11 , wherein: 
 the semi-solid metal alloy slurry comprises aluminum.    
   
   
       16 . The method of  claim 11 , wherein: 
 the mold comprises a sand mold.    
   
   
       17 . The method of  claim 11 , wherein: 
 the mold is fabricated by coating a wax material with a slurry.    
   
   
       18 . The method of  claim 11 , wherein: 
 a vacuum is applied to the mold cavity to pull the semi-solid metal alloy slurry into the mold cavity.    
   
   
       19 . A system for making cast metallic parts, comprising: 
 a furnace having a heated vessel suitable for holding liquid metal alloy;    a semi-solid slurry production machine for producing a low fraction solid semi-solid metal alloy slurry substantially free of dendritic solids;    a mold having a mold cavity for receiving the semi-solid metal alloy slurry at a low pressure; and    a metal transfer device adapted to transfer the semi-solid metal alloy slurry from the semi-solid slurry production machine to the mold.    
   
   
       20 . The system of  claim 19 , wherein: 
 the metal transfer device is robotic.    
   
   
       21 . The system of  claim 19 , wherein: 
 the semi-solid slurry production machine comprises an agitating member configured to agitate the liquid metal alloy.    
   
   
       22 . The system of  claim 21 , wherein: 
 the agitating member is rotatable.    
   
   
       23 . The system of  claim 20 , wherein: 
 the semi-solid metal alloy slurry comprises solids having a weight percentage of about one percent to about twenty percent.    
   
   
       24 . The system of  claim 20 , wherein: 
 the mold cavity receives the semi-solid metal alloy slurry at about atmospheric pressure.