Titanium alloy with improved properties

Abstract

A titanium alloy having high strength, fine grain size, and low cost and a method of manufacturing the same is disclosed. In particular, the titanium alloy offers 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 low cycle fatigue (LCF) maximum stress of at least about 970 MPa over about 25,000 cycles. The titanium alloy is particularly useful for a multitude of applications including components of aircraft engines. The titanium alloy comprises, in weight percent, about 6.0 to about 6.7% aluminum, about 1.4 to about 2.0% vanadium, about 1.4 to about 2.0% molybdenum, about 0.20 to about 0.42% silicon, about 0.17 to about 0.23% oxygen, maximum about 0.24% iron, maximum about 0.08% carbon and balance titanium with incidental impurities.

What is claimed is: 
     
         1 . A titanium alloy comprising, in weight %:
 aluminum from 6.0 to 6.7;   vanadium from 1.4 to 2.0;   molybdenum from 1.4 to 2.0;   silicon from 0.20 to 0.42;   oxygen from 0.17 to 0.23;   iron up to 0.24;   carbon up to 0.08; and   balance titanium with incidental impurities, wherein the 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. 
   
     
     
         2 . The titanium alloy of  claim 1 , wherein the alloy comprises at least one of:
 aluminum from about 6.3 to 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.   
     
     
         3 . The titanium alloy of  claim 1 , wherein the alloy comprises:
 aluminum from about 6.3 to 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;   carbon from about 0.01 to about 0.05; and   balance titanium with incidental impurities.   
     
     
         4 . The titanium alloy of  claim 1 , wherein the 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   the balance titanium with incidental impurities.   
     
     
         5 . The titanium alloy of  claim 1 , wherein the maximum concentration of any one impurity element present in the titanium alloy is 0.1 wt. % and the combined concentration of all impurities is less than or equal to 0.4 wt. %. 
     
     
         6 . The titanium alloy of  claim 1 , wherein a molybdenum equivalence (Mo eq ) of the alloy is 2.6 to 4.0 and the molybdenum equivalence is defined as: Mo eq =Mo+0.67V+2.9Fe. 
     
     
         7 . The titanium alloy of  claim 1 , wherein an aluminum equivalence (Al eq ) of the alloy is 10.6 to 12.9 and the aluminum equivalence is defined as: Al eq =Al+27O. 
     
     
         8 . The titanium alloy of  claim 1 , wherein:
 a molybdenum equivalence (Mo eq ) of the alloy is 2.6 to 4.0 and the molybdenum equivalence is defined as: Mo eq =Mo+0.67V+2.9Fe; and   an aluminum equivalence (Al eq ) of the alloy is 10.6 to about 12.9 and the aluminum equivalence is defined as: Al eq =Al+27O.   
     
     
         9 . The titanium alloy of  claim 1 , wherein an ultimate tensile strength (UTS) of the alloy is greater than 950 MPa (137 ksi), a tensile yield strength of the alloy is at least 1,000 MPa (145 ksi) and an elongation of the alloy is at least about 10%. 
     
     
         10 . The titanium alloy of  claim 9 , wherein the UTS is at least 1100 MPa (160 ksi). 
     
     
         11 . The titanium alloy of  claim 9 , wherein the alloy has a reduction of area (RA) of at least about 25% when evaluated using an ASTM E8 standard. 
     
     
         12 . The titanium alloy of  claim 1 , wherein a V50 ballistic limit of the alloy is at least 60 feet per second (18 m/s) greater than a base V50 ballistic limit measured for a T-64 alloy when a 0.616 inch (1.56 cm) thick plate of the alloy is tested against a 12.7 mm diameter steel fragment simulating projectile. 
     
     
         13 . The titanium alloy of  claim 1 , wherein the density of the alloy is between 4.4 g/cm 3  (0.161 lb./in 3 ) and 4.55 g/cm 3  (0.164 lb./in 3 ). 
     
     
         14 . The titanium alloy of  claim 1 , wherein the alloy comprises a beta transus temperature between 1010° C. (1850° F.) and 1040° C. (1904° F.). 
     
     
         15 . The titanium alloy of  claim 1 , wherein the alloy comprises a microstructure with a primary alpha phase in a background of a beta phase and an alpha grain size of less than or equal to 15 μm. 
     
     
         16 . A part formed from the alloy of  claim 1 . 
     
     
         17 . A titanium alloy comprising, in weight %:
 aluminum from about 6.3 to 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;   carbon from about 0.01 to about 0.05; and   balance titanium with incidental impurities, wherein the alloy comprises 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.   
     
     
         18 . The titanium alloy of  claim 17 , wherein the alloy consists essentially 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;   carbon at about 0.03; and   balance titanium with incidental impurities.   
     
     
         19 . A titanium alloy comprising, in weight %:
 aluminum from about 6.3 to 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;   carbon from about 0.01 to about 0.05; and   balance titanium with incidental impurities,   
       wherein:
 a molybdenum equivalence (Mo eq ) of the alloy is 2.6 to 4.0 and the molybdenum equivalence is defined as: Mo eq =Mo+0.67V+2.9Fe; 
 an aluminum equivalence (Al eq ) of the alloy is 10.6 to about 12.9 and the aluminum equivalence is defined as: Al eq =Al+27O; and 
 a room temperature longitudinal low cycle fatigue (LCF) maximum stress of the alloy is at least about 950 MPa over about 20,000. 
 
     
     
         20 . The titanium alloy of  claim 19 , wherein the alloy consists essentially 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;   carbon at about 0.03; and   balance titanium with incidental impurities.