Method of Making High Strength-High Stiffness Beta Titanium Alloy

Abstract

A method of making a high strength, high stiffness beta titanium alloy, comprising introducing boron into a beta titanium alloy to produce TiB precipitates; heat treating the titanium alloy with TiB precipitates by homogenization above the beta transus temperature of the alloy; subjecting the heat treated alloy to a hot metalworking operation below the beta transus temperature; heat treating the worked alloy with a solution treatment below the beta transus temperature; and ageing the solution treated alloy below the beta transus temperature.

1 . A method of making a high strength, high stiffness beta titanium alloy, comprising:
 introducing boron into a beta titanium alloy to produce TiB precipitates;   heat treating the titanium alloy with TiB precipitates by homogenization above the beta transus temperature of the alloy;   subjecting the heat treated alloy to a hot metalworking operation below the beta transus temperature;   heat treating the worked alloy with a solution treatment below the beta transus temperature; and   ageing the solution treated alloy below the beta transus temperature.   
     
     
         2 . The method of  claim 1  wherein the TiB precipitates are produced in the alloy by casting, cast-and-wrought processing, powder metallurgy techniques, e.g., gas atomization, or blended elemental approach. 
     
     
         3 . The method of  claim 2  wherein the boron is added to a molten titanium alloy and the liquid melt is atomized to obtain titanium alloy powder containing TiB precipitates, and the titanium alloy powder is consolidated to obtain a fully dense powder compact. 
     
     
         4 . The method of  claim 3  wherein the titanium alloy powder is consolidated by hot isostatic pressing. 
     
     
         5 . The method of  claim 1  wherein the beta transus temperature of the alloy is about 1580° F. and the alloy is heat treated by homogenization at a temperature range of about 1900-2200° F. for 2-4 hours. 
     
     
         6 . The method of  claim 5  wherein the hot metalworking is forging, rolling or extrusion at a temperature of about 1500° F. 
     
     
         7 . The method of  claim 6  wherein the heat treated alloy is extruded at a ram speed of approximately 120 inch/min. 
     
     
         8 . The method of  claim 7  wherein the heat treated alloy is extruded from a powder compact into a bar. 
     
     
         9 . The method of  claim 5  wherein the worked alloy is heat treated with a solution treatment at approximately 1500° F. for about 1 hour and cooled to room temperature. 
     
     
         10 . The method of  claim 9  wherein the heat treated and worked alloy is gas furnace cooled to room temperature at a cooling rate of about 200° F./minute. 
     
     
         11 . The method of  claim 9  wherein the solution treated alloy is aged at about 1100° F. for about 6 hours. 
     
     
         12 . The method of  claim 11  wherein the aged alloy is air cooled to room temperature. 
     
     
         13 . The method of  claim 1  wherein the heat treating of the titanium alloy by homogenization improves the tensile elongation while maintaining the tensile strength of the titanium alloy. 
     
     
         14 . The method of  claim 1  wherein the ageing of the solution treated alloy increases the tensile strength and tensile modulus of the alloy without a reduction in tensile elongation. 
     
     
         15 . The method of  claim 1  wherein the titanium alloy is Ti-5553. 
     
     
         16 . The method of  claim 5  wherein the titanium alloy is Ti-5553.