Semi-solid metal casting process and product

Abstract

A method for the refining of primary silicon in hypereutectic alloys by mixing a hypereutectic alloy and a solid/semi-solid hypoeutectic alloy is described. The method provides control of the morphology, size, and distribution of primary Si in a hypereutectic Al—Si casting by mixing a hypoeutectic Al—Si liquid with one that is hypereutectic to impart desirable mechanical properties.

What is claimed is:  
     
         1 . A semi-solid metal (SSM) casting process, comprising: 
 providing an Al—Si hypereutectic alloy and an Al—Si hypoeutectic alloy; 
 heating at least one of the Al—Si hypereutectic alloy or the Al—Si hypoeutectic alloy;  
 mixing the Al—Si hypereutectic alloy with the Al—Si hypoeutectic alloy;  
 cooling the hypereutectic alloy—hypoeutectic alloy mixture for a length of time to form a semi-solid metal; and,  
   casting the semi-solid metal.    
     
     
         2 . An SSM casting process according to  claim 1 , further comprising heating both the Al—Si hypereutectic alloy and the Al—Si hypoeutectic alloy.  
     
     
         3 . An SSM casting process according to  claim 2 , further comprising: 
 controlling the length of time to achieve a cooling rate by heating the Al—Si hypereutectic alloy to a predetermined temperature, heating the Al—Si hypoeutectic alloy to a predetermined temperature, and mixing the Al—Si hypereutectic alloy with the Al—Si hypoeutectic alloy.    
     
     
         4 . An SSM casting process according to  claim 3 , wherein the Al—Si hypereutectic alloy predetermined temperature is different from the Al—Si hypoeutectic alloy predetermined temperature.  
     
     
         5 . An SSM casting process according to  claim 3 , wherein the difference in temperature of the Al—Si hypoeutectic and hypereutectic alloys is chosen to achieve a faster rate of cooling of the hotter alloy as compared to heating the hotter Al—Si hypereutectic alloy and allowing the hotter alloy to cool independently at room temperature.  
     
     
         6 . An SSM casting process according to  claim 4 , wherein the difference in temperature is chosen to achieve a cast product having Si particles with an average diameter ranging from about  60  microns to about 100 microns.  
     
     
         7 . An SSM casting process according to  claim 6 , wherein the difference in temperature is chosen to achieve a cast product having Si particles with an average diameter of 70 microns or less.  
     
     
         8 . An SSM casting process according to  claim 6 , wherein the difference in temperature is chosen to achieve a cast product with Si particles that are more uniformly dispersed than a cast product made by a conventional SSM rheocasting process.  
     
     
         9 . An SSM casting process according to  claim 1 , wherein said hypereutectic alloy is greater than 12.6 percent Si.  
     
     
         10 . An SSM casting process according to  claim 9 , wherein said hypereutectic alloy is about 23 percent to about 25 percent Si.  
     
     
         11 . An SSM casting process according to  claim 1 , wherein said hypoeutectic alloy is less than about 12.6 percent Si.  
     
     
         12 . An SSM casting process according to  claim 11 , wherein said hypoeutectic alloy is about 7 percent to about 8 percent Si.  
     
     
         13 . An SSM casting process according to  claim 12 , wherein said hypoeutectic alloy is about 7 percent Si.  
     
     
         14 . An SSM casting process according to  claim 2 , wherein the temperature of said hypereutectic alloy ranges from about 800° C. and about 900° C.  
     
     
         15 . An SSM casting process according to  claim 14 , wherein the temperature of said hypereutectic alloy is 800° C.  
     
     
         16 . An SSM casting process according to  claim 2 , wherein the temperature of said hypoeutectic alloy ranges from about 350° C. and about 850° C.  
     
     
         17 . An SSM casting process according to  claim 16 , wherein the temperature of said hypoeutectic alloy is about 500° C.  
     
     
         18 . An SSM cast product that is manufactured by an SSM casting process, comprising Si particles having less than an average diameter of about 100 microns.  
     
     
         19 . A cast product according to  claim 18 , wherein the rate of cooling of the Al—Si alloy yields Si particles in the cast product that have less than an average diameter ranging from about 60 microns to about 100 microns.  
     
     
         20 . A cast product according to  claim 19 , wherein the Si particles have less than an average diameter of about 70 microns or less.  
     
     
         21 . A cast product according to  claim 18 , wherein the rate of cooling of the Al—Si alloy yields Si particles in the cast product that are more uniformly dispersed than a cast product made by a conventional SSM rheocasting process.