Processing of alpha-beta titanium alloys

Abstract

A method for increasing tensile strength of a cold workable alpha-beta titanium alloy comprises solution heat treating a cold workable alpha-beta titanium alloy in a temperature range of T β −106° C. to T β −72.2° C. for 15 minutes to 2 hours; cooling the alpha-beta titanium alloy at a cooling rate of at least 3000° C./minute; cold working the alpha-beta titanium alloy to impart an effective strain in the range of 5 percent to 35 percent in the alloy; and aging the alpha-beta titanium alloy in a temperature range of T β −669° C. to T β −517° C. for 1 to 8 hours. Fastener stock and fasteners including solution treated, quenched, cold worked, and aged alpha-beta titanium alloys are also disclosed.

What is claimed is: 
     
         1 . A method for producing an alpha-beta titanium alloy fastener stock, comprising:
 heating an alpha-beta titanium alloy in a temperature range of 866° C. to 899° C. for 15 minutes to 2 hours;   water quenching the alpha-beta titanium alloy;   cold working the alpha-beta titanium alloy using at least one of cold drawing and cold swaging the alpha-beta titanium alloy to impart an effective strain in the range of 5 percent to 35 percent to the alpha-beta titanium alloy; and   aging the alpha-beta titanium alloy in a temperature range of 302° C. to 454° C. for 1 to 8 hours;   wherein the alpha-beta titanium alloy comprises, in percentages by weight based on total alloy weight:
 2.9 to 5.0 aluminum; 
 2.0 to 3.0 vanadium; 
 0.4 to 2.0 iron; 
 0.2 to 0.3 oxygen; 
 0.005 to 0.3 carbon; 
 titanium; 
 impurities; and 
   optionally, one or more of tin, zirconium, molybdenum, chromium, nickel, silicon, copper, niobium, tantalum, manganese, cobalt, boron and yttrium;   wherein the sum of the weight percentages of any tin, zirconium, molybdenum, chromium, nickel, silicon, copper, niobium, tantalum, manganese, cobalt, boron, and yttrium present in the titanium alloy is less than 0.5 weight percent;   wherein the individual concentrations of any tin, zirconium, molybdenum, chromium, nickel, silicon, copper, niobium, tantalum, manganese, and cobalt present in the alloy are each no greater than 0.1 weight percent;   wherein the individual concentrations of any boron and yttrium present in the alloy are each less than 0.005 weight percent.   
     
     
         2 . The method of  claim 1 , wherein cold working the alpha-beta titanium alloy comprises working the alpha-beta titanium alloy at temperatures less than 676.7° C. 
     
     
         3 . The method of  claim 1 , wherein cold working the alpha-beta titanium alloy comprises working the alpha-beta titanium alloy at temperatures less than 537.8° C. 
     
     
         4 . The method of  claim 1 , wherein cold working the alpha-beta titanium alloy comprises imparting an effective strain in the range of 10 percent to 30 percent to the alpha-beta titanium alloy. 
     
     
         5 . The method of  claim 1 , wherein cold working the alpha-beta titanium alloy comprises imparting an effective strain in the range of 13 percent to 23 percent to the alpha-beta titanium alloy. 
     
     
         6 . The method of  claim 1 , wherein heating the alpha-beta titanium alloy comprises heating the alpha-beta titanium alloy in a temperature range of 874° C. to 888° C. for 30 minutes to 1 hour. 
     
     
         7 . The method of  claim 1 , wherein aging the alpha-beta titanium alloy temperature comprises heating the alpha-beta titanium alloy in a temperature range of 349° C. to 391° C. for 1 to 5 hours. 
     
     
         8 . The method of  claim 1 , further comprising, prior to heating the alpha-beta titanium alloy, hot working the alpha-beta titanium alloy. 
     
     
         9 . The method of  claim 8 , wherein hot working the alpha-beta titanium alloy comprises working the alpha-beta titanium alloy in a temperature range of 888° C. to 943° C. 
     
     
         10 . The method of  claim 8 , wherein hot working the alpha-beta titanium alloy comprises rolling the alpha-beta titanium alloy to a diameter in a range of 0.635 cm to 5.08 cm. 
     
     
         11 . The method of  claim 8 , further comprising, subsequent to hot working the alpha-beta titanium alloy, cutting the alpha-beta titanium alloy into straight lengths. 
     
     
         12 . The method of  claim 1 , further comprising, intermediate quenching the alpha-beta titanium alloy and cold working the alpha-beta titanium alloy, surface conditioning the alpha-beta titanium alloy. 
     
     
         13 . The method of  claim 1 , further comprising, intermediate cold working the alpha-beta titanium alloy and aging the alpha-beta titanium alloy, surface conditioning the alpha-beta titanium alloy. 
     
     
         14 . The method of  claim 1 , further comprising, after at least one of cold working the alpha-beta titanium alloy and aging the alpha-beta titanium alloy, finishing the alpha-beta titanium alloy. 
     
     
         15 . The method of  claim 14 , wherein finishing the alpha-beta titanium alloy comprises machining the alpha-beta titanium alloy. 
     
     
         16 . An article of manufacture selected from a titanium alloy fastener and titanium alloy fastener stock, the article of manufacture including a hot rolled, solution treated, and cold worked alpha-beta titanium alloy comprising, in percentages by weight based on total alloy weight:
 2.9 to 5.0 aluminum;   2.0 to 3.0 vanadium;   0.4 to 2.0 iron;   0.2 to 0.3 oxygen;   0.005 to 0.3 carbon;   titanium;   impurities; and   optionally, one or more of tin, zirconium, molybdenum, chromium, nickel, silicon, copper, niobium, tantalum, manganese, cobalt, boron and yttrium;   wherein the sum of the weight percentages of any tin, zirconium,   molybdenum, chromium, nickel, silicon, copper, niobium, tantalum, manganese, cobalt, boron, and yttrium present in the titanium alloy is less than 0.5 weight percent;   wherein the individual concentrations of any tin, zirconium, molybdenum, chromium, nickel, silicon, copper, niobium, tantalum, manganese, and cobalt present in the alloy are each no greater than 0.1 weight percent;   wherein the individual concentrations of any boron and yttrium present in the alloy are each less than 0.005 weight percent.   
     
     
         17 . The article of manufacture of  claim 16 , wherein the alpha-beta titanium alloy is a hot rolled, solution treated, cold worked, and aged alpha-beta titanium alloy. 
     
     
         18 . The article of manufacture of  claim 16 , wherein the article of manufacture is a titanium alloy fastener selected from a bolt, a nut, a stud, a screw, a washer, a lock washer, and a rivet. 
     
     
         19 . The article of manufacture of  claim 17 , wherein the article of manufacture is a titanium alloy fastener selected from a bolt, a nut, a stud, a screw, a washer, a lock washer, and a rivet. 
     
     
         20 . The article of manufacture according to  claim 16 , wherein the article of manufacture is a straight length of fastener stock. 
     
     
         21 . The article of manufacture according to  claim 17 , wherein the article of manufacture is a straight length of fastener stock.