Titanium alloy with improved properties

Abstract

A method of manufacturing a titanium alloy part with a composition, in weight %, of aluminum from about 6.0 to about 6.7; vanadium from about 1.4 to about 2.0; molybdenum from about 1.4 to about 2.0; silicon from about 0.20 to about 0.35; oxygen from about 0.18 to about 0.23; iron from about 0.16 to about 0.24; carbon from about 0.02 to about 0.06; and balance titanium, is provided. The method includes a first heat treatment on an ingot of the titanium alloy, forging of the ingot to break down the cast structure, a second heat treatment on the forged ingot, rolling the forged ingot to a plate, bar or billet, and annealing the plate, bar or billet below the beta transus temperature of the titanium alloy. The first and second heat treatments are between 40 and 200° C. and between 30 and 100° C. below the beat transus temperature, respectively.

What is claimed is: 
     
         1 . A method of manufacturing a titanium alloy part, comprising:
 a. performing a first heat treatment on an ingot of a titanium alloy at a temperature between 40 and 200 degrees Centigrade above the beta transus temperature of the titanium alloy, forging the ingot to break down the cast structure of the ingot, and then cooling the forged ingot, wherein the titanium alloy comprises in weight percent (wt. %):   aluminum from about 6.0 to about 6.7;   vanadium from about 1.4 to about 2.0;   molybdenum from about 1.4 to about 2.0;   silicon from about 0.20 to about 0.35;   oxygen from about 0.18 to about 0.23;   iron from about 0.16 to about 0.24;   carbon from about 0.02 to about 0.06; and   balance titanium with incidental impurities;   b. performing a second heat treatment on the forged ingot at a temperature between 30 and 100 degrees Centigrade below the beta transus temperature and rolling the forged ingot to a plate, bar, or billet; and   c. annealing the plate, bar or billet of the titanium alloy at a temperature below the beta transus temperature.   
     
     
         2 . The method of  claim 1 , further comprising the step of reheating the forged ingot to a temperature between 50 and 150 degrees Centigrade above the beta transus temperature to allow recrystallization of the beta phase. 
     
     
         3 . The method of  claim 1 , further comprising the step of reheating the forged ingot to a temperature between 30 to 150 degrees Centigrade above the beta transus temperature to allow recrystallization of the beta phase, then forging to a strain of at least 10 percent and water quenching. 
     
     
         4 . The method of  claim 1 , wherein the titanium alloy consists of at least one of:
 aluminum from about 6.3 to about 6.7;   vanadium from about 1.5 to about 1.9;   molybdenum from about 1.5 to about 1.9;   silicon from about 0.34 to about 0.38;   oxygen from about 0.18 to about 0.21;   iron from about 0.1 to about 0.2; and   carbon from about 0.01 to about 0.05.   
     
     
         5 . The method of  claim 1 , wherein the titanium alloy consists of at least one of:
 aluminum at about 6.5;   vanadium at about 1.7;   molybdenum at about 1.7;   silicon at about 0.36;   oxygen at about 0.2;   iron at about 0.16; and   carbon at about 0.03.   
     
     
         6 . The method of  claim 1 , wherein the maximum concentration of any one impurity element present in the alloy is 0.1 wt. % and the combined concentration of all impurities is less than or equal to 0.4 wt. %. 
     
     
         7 . The method of  claim 1 , wherein the titanium alloy comprises at least one of:
 a molybdenum equivalence (Mo eq ) of 2.6 to 4.0, wherein the molybdenum equivalence is defined as: Mo eq =Mo+0.67V+2.9Fe; and   an aluminum equivalence (Al eq ) of 10.6 to about 12.9, wherein the aluminum equivalence is defined as: Al eq =Al+27O.   
     
     
         8 . The method of  claim 1 , wherein the annealed plate, bar or billet of the titanium alloy further comprises at least one of:
 an ultimate tensile strength (UTS) greater than 950 MPa;   a tensile yield strength of at least 1,000 MPa;   an elongation of at least 10%;   a V50 ballistic limit that is at least 80 feet per second greater than a base V50 ballistic limit measured for a T-64 alloy when a 0.616 inch thick plate is tested against a 12.7 mm diameter steel fragment simulating projectile; and   a reduction of area (RA) of at least 25% of an original cross-sectional area of a tensile sample of the annealed alloy after fracture when evaluated using ASTM E8 standard.   
     
     
         9 . The method of  claim 1 , wherein the annealed plate, bar or billet of the titanium alloy further comprises:
 a UTS of at least 1,100 MPa;   a tensile yield strength of at least 1,000 MPa;   an elongation of at least 10%;   a V50 ballistic limit that is at least 60 feet per second greater than a base V50 ballistic limit measured for a T-64 alloy when a 0.616 inch thick plate is tested against a 12.7 mm diameter steel fragment simulating projectile; and   a reduction of area (RA) of at least 25% of an original cross-sectional area of a tensile sample of the annealed alloy after fracture when evaluated using ASTM E8 standard.   
     
     
         10 . The method of  claim 1 , wherein the annealed plate, bar or billet of the titanium alloy comprises at least one of:
 a room temperature longitudinal low cycle fatigue (LCF) maximum stress of at least about 950 MPa over about 20,000 cycles; and   a room temperature transverse LCF maximum stress of at least about 970 MPa over about 25,000 cycles.   
     
     
         11 . The method of  claim 1 , wherein the annealed plate, bar or billet of the titanium alloy comprises a density between 4.4 g/cm 3  (0.161 lb./in 3 ) and 4.55 g/cm 3  (0.164 lb./in 3 ). 
     
     
         12 . The method of  claim 1 , wherein the beta transus temperature is between 1010° C. and 1040° C. 
     
     
         13 . The method of  claim 1 , wherein the annealed plate, bar or billet of the titanium alloy comprises a microstructure with a primary alpha phase in a background of beta phase. 
     
     
         14 . The method of  claim 1 , wherein the annealed plate, bar or billet of the titanium alloy comprises a primary alpha phase with an alpha grain size of less than or equal to 15 μm. 
     
     
         15 . An aviation component formed by the method of  claim 1 . 
     
     
         16 . A fan blade formed by the method of  claim 1 . 
     
     
         17 . A method of manufacturing a titanium alloy part, comprising:
 a. performing a first heat treatment on an ingot of a titanium alloy at a temperature between 40 and 200 degrees Centigrade above the beta transus temperature of the titanium alloy and forging the ingot to break down the cast structure of the ingot and then cooling the forged ingot, wherein the titanium alloy comprises in weight percent (wt. %):
 aluminum from about 6.0 to about 6.7; 
 vanadium from about 1.4 to about 2.0; 
 molybdenum from about 1.4 to about 2.0; 
 silicon from about 0.20 to about 0.35; 
 oxygen from about 0.18 to about 0.23; 
 iron from about 0.16 to about 0.24; 
 carbon from about 0.02 to about 0.06; and 
 balance titanium with incidental impurities; 
   b. performing a second heat treatment on the forged ingot at a temperature between 30 and 100 degrees Centigrade below the beta transus temperature and rolling the forged ingot to a plate, bar, or billet; and   c. annealing the plate, bar, or billet at a temperature below the beta transus temperature;   wherein the annealed plate, bar, or billet comprises:
 a UTS greater than 950 MPa; 
 a tensile yield strength of at least 1,000 MPa; 
 an elongation of at least 10%; 
 a reduction of area (RA) of at least 25% of the original cross-sectional area of a tensile sample the annealed alloy after fracture when evaluated using ASTM E8 standard; and at least one of: 
 a V50 ballistic limit that is at least 80 feet per second greater than a base V50 ballistic limit measured for a T-64 alloy when a 0.616 inch thick plate is tested against a 12.7 mm diameter steel fragment simulating projectile; and 
 a V50 ballistic limit that is at least 60 feet per second greater than a base V50 ballistic limit measured for a T-64 alloy when a 0.616 inch thick plate is tested against a 12.7 mm diameter steel fragment simulating projectile. 
   
     
     
         18 . The method of  claim 17 , wherein the titanium alloy comprises:
 aluminum at about 6.5;   vanadium at about 1.7;   molybdenum at about 1.7;   silicon at about 0.36;   oxygen at about 0.2;   iron at about 0.16;   carbon at about 0.03; and   balance titanium with incidental impurities;   
     
     
         19 . A method of manufacturing a titanium alloy part, comprising:
 a. performing a first heat treatment on an ingot of a titanium alloy at a temperature between 40 and 200 degrees Centigrade above the beta transus temperature of the titanium alloy, forging the ingot to break down the cast structure of the ingot and then cooling the forged ingot, wherein the titanium alloy comprises in weight percent (wt. %):
 aluminum from about 6.3 to about 6.7; 
 vanadium from about 1.5 to about 1.9; 
 molybdenum from about 1.5 to about 1.9; 
 silicon from about 0.34 to about 0.38; 
 oxygen from about 0.18 to about 0.21; 
 iron from about 0.1 to about 0.2; and 
 carbon from about 0.01 to about 0.05; and 
 balance titanium with incidental impurities; 
   b. performing a second heat treatment of the forged ingot at a temperature between 30 and 100 degrees Centigrade below the beta transus temperature of the titanium alloy and rolling the titanium alloy to a plate, bar, or billet; and   c. annealing the plate, bar or billet of the titanium alloy at a temperature below the beta transus temperature.   
     
     
         20 . The method of  claim 19 , wherein the annealed plate, bar, or billet comprises:
 a UTS greater than 950 MPa;   a tensile yield strength of at least 1,000 MPa;   an elongation of at least 10%;   a reduction of area (RA) of at least 25% of the original cross-sectional area of a tensile sample the annealed alloy after fracture when evaluated using ASTM E8 standard;   and at least one of:
 a V50 ballistic limit that is at least 80 feet per second greater than a base V50 ballistic limit measured for a T-64 alloy when a 0.616 inch thick plate is tested against a 12.7 mm diameter steel fragment simulating projectile; and 
 a V50 ballistic limit that is at least 60 feet per second greater than a base V50 ballistic limit measured for a T-64 alloy when a 0.616 inch thick plate is tested against a 12.7 mm diameter steel fragment simulating projectile.