Treatment Method Of Foil, Production Method Of Foil, And Foil

Abstract

A production method of a foil includes a foil forming step of processing a titanium alloy material made of a titanium alloy containing tantalum to form a foil and a foil treatment step of treating the foil. The foil treatment step includes a recrystallization heating step of heating the foil under vacuum or under an inert gas atmosphere to recrystallize a structure of the foil, and a foil treatment cooling step of, after the recrystallization heating step, cooling the foil at a cooling rate that is higher than or equal to a cooling rate in which a temperature of the foil decreases by −150° C. per 10 minutes within a range until the temperature of the foil reaches 600° C. under vacuum or under an inert gas atmosphere to suppress growth of crystal grains in the structure of the foil, the growth being associated with the recrystallization.

What is claimed is: 
     
         1 . A production method of a foil comprising:
 a foil forming step of processing a titanium alloy material made of a titanium alloy containing tantalum to form a foil; and   a foil treatment step of treating the foil, wherein:   the foil forming step includes
 a rolling step of rolling the titanium alloy material to form a foil, 
 an annealing step of annealing the titanium alloy material, which has been subjected to the rolling step, at an annealing temperature for annealing, and 
 a foil formation cooling step of cooling the titanium alloy material that has been subjected to the annealing step; and 
   the foil treatment step includes
 a recrystallization heating step of heating the foil under vacuum or under an inert gas atmosphere to recrystallize a structure of the foil, and 
 a foil treatment cooling step of, after the recrystallization heating step, cooling the foil at a cooling rate that is higher than or equal to a cooling rate in which a temperature of the foil decreases by −150° C. per 10 minutes within a range until the temperature of the foil reaches 600° C. under vacuum or under an inert gas atmosphere to suppress growth of crystal grains in the structure of the foil, the growth being associated with the recrystallization. 
   
     
     
         2 . A production method of a foil comprising:
 a foil forming step of processing a titanium alloy material made of a titanium alloy containing tantalum to form a foil; and   a foil treatment step of treating the foil, wherein:   the foil forming step includes
 a rolling step of rolling the titanium alloy material to form a foil, 
 an annealing step of annealing the titanium alloy material, which has been subjected to the rolling step, at an annealing temperature for annealing, and 
 a foil formation cooling step of cooling the titanium alloy material that has been subjected to the annealing step; and 
   the foil treatment step includes
 a recrystallization heating step of heating the foil under vacuum or under an inert gas atmosphere to recrystallize a structure of the foil, and 
 a foil treatment cooling step of, after the recrystallization heating step, cooling the foil by forced cooling in which a temperature of the foil is lowered more quickly than in a case of natural cooling under vacuum or under an inert gas atmosphere to suppress growth of crystal grains in the structure of the foil, the growth being associated with the recrystallization. 
   
     
     
         3 . The production method of a foil according to  claim 1 , wherein the titanium alloy contains 15 at % to 27 at % of tantalum, 1 at % to 8 at % of tin, and 0.4 at % to 1.7 at % of oxygen when the entire titanium alloy is defined as 100 at %, and a remaining portion is composed of titanium and inevitable impurities. 
     
     
         4 . The production method of a foil according to  claim 1 , wherein:
 the foil forming step includes, prior to the rolling step, a processing step of processing the titanium alloy material at least once; and   the processing step includes
 a second rolling step of rolling the titanium alloy material to thin a thickness of the titanium alloy material, 
 a second annealing step of annealing the titanium alloy material, which has been subjected to the second rolling step, at an annealing temperature for annealing, and 
 a second foil formation cooling step of cooling the titanium alloy material that has been subjected to the second annealing step. 
   
     
     
         5 . The production method of a foil according to  claim 1 , wherein an average particle diameter by an area weighted average of crystal grains contained in the foil or a number of crystal grains aligned in a thickness direction of the foil is controlled by adjusting a rolling reduction ratio in the rolling step. 
     
     
         6 . The production method of a foil according to  claim 1 , wherein a vacuum degree under vacuum is 1×10 −2  (Pa) or less. 
     
     
         7 . The production method of a foil according to  claim 1 , wherein a heating temperature of the foil in the recrystallization heating step is in a range of 700 to 900° C. 
     
     
         8 . The production method of a foil according to  claim 1 , wherein:
 the recrystallization heating step is performed in a furnace having a housing unit configured to be able to house the foil, a vacuum generation unit configured to vacuumize an inside of the housing unit, and a heating unit configured to heat the housing unit; and   the foil treatment cooling step involves externally cooling the housing unit that houses the foil under an inert gas atmosphere or under vacuum to cool the foil.   
     
     
         9 . The production method of a foil according to  claim 1 , wherein a ratio of an α phase contained in the foil after the foil treatment cooling step is 10% or less, and a ratio of a β phase is 90% or more. 
     
     
         10 . The production method of a foil according to  claim 1 , wherein an average particle diameter by an area weighted average of crystal grains contained in the foil or a number of crystal grains aligned in a thickness direction of the foil is controlled by adjusting a heating temperature in the recrystallization heating step. 
     
     
         11 . A foil made of a titanium alloy, wherein:
 the titanium alloy contains 15 at % to 27 at % of tantalum, 1 at % to 8 at % of tin, and 0.4 at % to 1.7 at % of oxygen when the entire titanium alloy is defined as 100 at % and a remaining portion is composed of titanium and inevitable impurities;   an average particle diameter by an area weighted average of crystal grains contained in the foil is in a range of 8.7 μm or more and 16.5 μm or less; and   a ratio of an α phase contained in the foil is 10% or less and a ratio of a β phase is 90% or more.   
     
     
         12 . The production method of a foil according to  claim 2 , wherein the titanium alloy contains 15 at % to 27 at % of tantalum, 1 at % to 8 at % of tin, and 0.4 at % to 1.7 at % of oxygen when the entire titanium alloy is defined as 100 at %, and a remaining portion is composed of titanium and inevitable impurities. 
     
     
         13 . The production method of a foil according to  claim 2 , wherein:
 the foil forming step includes, prior to the rolling step, a processing step of processing the titanium alloy material at least once; and   the processing step includes
 a second rolling step of rolling the titanium alloy material to thin a thickness of the titanium alloy material, 
 a second annealing step of annealing the titanium alloy material, which has been subjected to the second rolling step, at an annealing temperature for annealing, and 
 a second foil formation cooling step of cooling the titanium alloy material that has been subjected to the second annealing step. 
   
     
     
         14 . The production method of a foil according to  claim 2 , wherein an average particle diameter by an area weighted average of crystal grains contained in the foil or a number of crystal grains aligned in a thickness direction of the foil is controlled by adjusting a rolling reduction ratio in the rolling step. 
     
     
         15 . The production method of a foil according to  claim 2 , wherein a vacuum degree under vacuum is 1×10 −2  (Pa) or less. 
     
     
         16 . The production method of a foil according to  claim 2 , wherein a heating temperature of the foil in the recrystallization heating step is in a range of 700 to 900° C. 
     
     
         17 . The production method of a foil according to  claim 2 , wherein:
 the recrystallization heating step is performed in a furnace having a housing unit configured to be able to house the foil, a vacuum generation unit configured to vacuumize an inside of the housing unit, and a heating unit configured to heat the housing unit; and   the foil treatment cooling step involves externally cooling the housing unit that houses the foil under an inert gas atmosphere or under vacuum to cool the foil.   
     
     
         18 . The production method of a foil according to  claim 2 , wherein a ratio of an α phase contained in the foil after the foil treatment cooling step is 10% or less, and a ratio of a β phase is 90% or more. 
     
     
         19 . The production method of a foil according to  claim 2 , wherein an average particle diameter by an area weighted average of crystal grains contained in the foil or a number of crystal grains aligned in a thickness direction of the foil is controlled by adjusting a heating temperature in the recrystallization heating step.