Method for improving the ductility of high-strength nanophase alloys

Abstract

A method for consolidating nanophase metal powder includes the steps of consolidating the powder by applying pressure to the powder at a first temperature, encompassing the powder with a flowable pressure transmitting medium that is heated to a second temperature that is higher than the first temperature, and compressing the heated medium and thereby further consolidating the powder. The first consolidating step may include encompassing the nanophase metal powder with a flowable pressure transmitting medium that is heated to the first temperature, and compressing the heated medium at the first temperature.

1 - 12 . (canceled)  
     
     
         13 . A method for consolidating a shaped nanophase metal powder, comprising the steps of: 
 encompassing said shaped nanophase metal powder with a flowable pressure transmitting medium that is heated to a first temperature;    compressing said heated medium at said first temperature and thereby consolidating said shaped nanophase metal powder;    heating said medium to a second temperature that is higher than said first temperature; and    compressing said heated medium at said second temperature and thereby further consolidating said shaped nanophase metal powder.    
     
     
         14 . The method according to  claim 13 , wherein said second temperature ranges between about 700° F. and about 1000° F.  
     
     
         15 . The method according to  claim 14 , wherein said second temperature ranges between about 775° F. and about 875° F.  
     
     
         16 . The method according to  claim 13 , wherein said first temperature ranges between about 700° F. and about 1000° F.  
     
     
         17 . The method according to  claim 16 , wherein said first temperature is about 700° F.  
     
     
         18 . The method according to  claim 13 , wherein said each compressing step comprises mechanically compacting said heated medium to consolidate said powder.  
     
     
         19 . The method according to  claim 18 , wherein said mechanically compacting is performed using a hydraulic press.  
     
     
         20 . The method according to  claim 13 , wherein said shaped powder is shaped by enclosing said powder in a container, said powder remaining enclosed in a said container during said encompassing step during which said container is also encompassed with said medium.  
     
     
         21 . The method according to  claim 20 , wherein said container is formed of a material tat is sufficiently thin to have a negligible effect on consolidating said powder when said medium is compressed.  
     
     
         22 . The method according to  claim 13 , further comprising: 
 prior to said consolidating step, cryomilling and degassing said powder.    
     
     
         23 . The method according to  claim 13 , wherein said powder is a nanophase metal selected from the group consisting of aluminum, iron, aluminum alloys, and iron alloys.  
     
     
         24 . The method according to  claim 23 , wherein said powder is nanophase aluminum.  
     
     
         25 . The method according to  claim 13 , wherein said shaped powder is a preform mass.