Nanocrystalline titanium alloy, and method and apparatus for manufacturing the same

Abstract

A method and apparatus for manufacturing a nanocrystalline titanium alloy by performing an equal channel angular pressing process to a titanium alloy material, and a nanocrystalline titanium alloy manufactured using the method and apparatus. The method for manufacturing the nanocrystalline titanium alloy includes steps of preparing a titanium alloy material, and performing an equal channel angular pressing process on the titanium alloy material at an isothermal condition of 575° C. to 625° C. The nanocrystalline titanium alloy according to has a grain size of 300 nm.

1 . A method for manufacturing a nanocrystalline titanium alloy comprising steps of: 
 preparing a titanium alloy material; and    performing an ECAP (equal channel angular pressing) process to the titanium alloy material at an isothermal condition of 575° C. to 625° C.    
   
   
       2 . The method of  claim 1 , wherein the ECAP process has a process rate of 0.4 mm/s to 2 mm/s.  
   
   
       3 . The method of  claim 2 , wherein the ECAP process has a process rate of 1.3 mm/s to 2 mm/s.  
   
   
       4 . The method of  claim 1 , wherein a total effective strain of the ECAP process is 1 to 8.  
   
   
       5 . The method of  claim 1 , comprising performing the ECAP process at least twice.  
   
   
       6 . The method of  claim 5 , comprising rotating the titanium alloy material by a predetermined rotation angle with respect to a previous ECAP process centering around a central axis passing through a center of an inlet of the channel, from a second ECAP process.  
   
   
       7 . The method of  claim 6 , wherein the rotation angle is substantially 180°.  
   
   
       8 . The method of  claim 7 , comprising performing the ECAP process an even number of times.  
   
   
       9 . The method of  claim 1 , further comprising preheating the titanium alloy material at a temperature of 575° C. to 625° C. for 7 minutes 30 seconds to 12 minutes 30 seconds, between the preparing of the titanium alloy material and the performing of the ECAP process.  
   
   
       10 . The method of  claim 1 , wherein the titanium alloy material comprises titanium as a main material and aluminum at 6 weight %, vanadium at 4 weight %, and other impurities.  
   
   
       11 . The method of  claim 10 , wherein an initial microstructure of the titanium alloy material is an equiaxed crystal structure or a lamellar structure.  
   
   
       12 . A nanocrystalline titanium alloy manufactured by the method of  claim 1 , wherein the nanocrystalline has a grain size of 300 nm or less.  
   
   
       13 . The nanocrystalline titanium alloy of  claim 12 , wherein the nanocrystalline titanium alloy comprises a mixture of alpha phases and beta phases and the beta phases are segmented and distributed in the entire microstructure of the nanocrystalline titanium alloy.  
   
   
       14 . The nanocrystalline titanium alloy of  claim 13 , wherein the nanocrystalline titanium alloy has a maximum elongation of 300% or more.  
   
   
       15 . The nanocrystalline titanium alloy of  claim 13 , wherein the nanocrystalline titanium alloy has a strain-rate sensitivity exponent of 0.4 or less.  
   
   
       16 . The nanocrystalline titanium alloy of  claim 13 , wherein the nanocrystalline titanium alloy has a superplastic forming temperature of 575° C. to 725° C.  
   
   
       17 . An apparatus for manufacturing a nanocrystalline titanium alloy, comprising: 
 an ECAP unit including a bent channel;    a temperature holding unit surrounding the ECAP unit and including at least one heating member for heating the ECAP unit to a predetermined temperature; and    a temperature measuring unit for measuring the temperature of the ECAP unit.    
   
   
       18 . The apparatus of  claim 17 , further comprising an adiabatic unit provided on a lower portion of the temperature holding unit.  
   
   
       19 . The apparatus of  claim 18 , wherein the adiabatic unit comprises asbestos.  
   
   
       20 . The apparatus of  claim 17 , wherein an inner contact angle of the bent portion of the channel is 90° and the outer arc angle thereof is 40°.