Thermo-mechanical process to enhance the quality of grain boundary networks in metal alloys

Abstract

Methods to enhance the quality of grain boundary networks are described. The process can result in the production of a metal including a relatively large fraction of special grain boundaries (e.g., a fraction of special grain boundaries of at least about 55%).

What is claimed is: 
     
         1 . A method of processing a metal alloy, comprising:
 while maintaining the metal alloy at a temperature expressed in Kelvins of at least about 0.95 times the solvus temperature of the metal alloy expressed in Kelvins:
 applying a force to strain the metal alloy over a first period of time; and 
 reducing the applied force over a second period of time subsequent to the first period of time; 
   wherein the metal alloy is processed to have a special grain boundary fraction of at least about 55%.   
     
     
         2 . A method as in  claim 1 , wherein the metal is processed to have a special grain boundary fraction of at least about 60%. 
     
     
         3 . (canceled) 
     
     
         4 . A method as in  claim 1 , wherein the temperature expressed in Kelvins is between about 0.95 times and about 1.05 times the solvus temperature of the metal alloy expressed in Kelvins. 
     
     
         5 . A method as in  claim 1 , wherein the metal alloy comprises a face-centered cubic metal with a stacking fault energy of less than about 100 mJ/m 2 . 
     
     
         6 . A method as in  claim 1 , wherein the largest component of the metal alloy, by mass, is copper. 
     
     
         7 . A method as in  claim 1 , wherein the metal alloy comprises at least about 75 wt % copper. 
     
     
         8 . A method as in  claim 1 , wherein the metal alloy comprises chromium as a minority component. 
     
     
         9 . A method as in  claim 1 , wherein the reducing step comprises reducing the applied force to zero. 
     
     
         10 . A method as in  claim 1 , wherein the reducing step comprises reducing the applied force to a non-zero value. 
     
     
         11 . A method as in  claim 1 , further comprising heating the metal alloy above the temperature prior to maintaining the metal alloy above the temperature. 
     
     
         12 . A method as in  claim 1 , further comprising, while maintaining the metal alloy at a temperature expressed in Kelvins of at least about 0.95 times the solvus temperature of the metal alloy expressed in Kelvins, applying a second force to strain the metal alloy over a third period of time subsequent to the first and second periods of time, and reducing the applied second force over a fourth period of time subsequent to the third period of time. 
     
     
         13 - 14 . (canceled) 
     
     
         15 . A method as in  claim 1 , wherein the first period of time is at least about 0.01 seconds. 
     
     
         16 . A method as in  claim 1 , wherein the second period of time is at least about 0.01 seconds. 
     
     
         17 . A method as in  claim 1 , wherein the applied force produces an engineering strain of at least about 3%. 
     
     
         18 . A method as in  claim 1 , wherein the applied force produces a von Mises strain of at least about 3%. 
     
     
         19 . A method as in  claim 1 , wherein the applied force produces a cumulative engineering strain of at least about 10%. 
     
     
         20 . A method as in  claim 1 , wherein the applied force produces a rate of strain of at least about 0.01% per second. 
     
     
         21 . A method as in  claim 1 , wherein the metal alloy comprises zirconium as a minority component. 
     
     
         22 . A method as in  claim 1 , wherein the metal alloy is processed to have a special grain boundary fraction of at least about 65%. 
     
     
         23 . A method as in  claim 1 , wherein the metal alloy is maintained at a temperature at which recrystallization of the metal alloy can occur.