Nanostructured Titanium Alloy and Method For Thermomechanically Processing The Same

Abstract

A nanostructured titanium alloy article is provided. The nanostructured alloy includes a developed titanium structure having at least 80% of grains of a grain size ≦1.0 microns.

What is claimed is: 
     
         1 . A nanostructured titanium alloy article, comprising:
 a developed titanium structure having ≧80% of grains being of a size ≦1.0 micron.   
     
     
         2 . The nanostructured titanium alloy article according to  claim 1 , wherein the developed titanium structure is a developed α-titanium structure. 
     
     
         3 . The nanostructured titanium alloy article according to  claim 1 , wherein the grains are α phase grains. 
     
     
         4 . The nanostructured titanium alloy article according to  claim 1 , wherein the developed titanium structure has a dislocation density ≧10 15  m −2 . 
     
     
         5 . The nanostructured titanium alloy article according to  claim 1 , wherein 20-40% of the grains include high angle grain boundaries with a misorientation angle ≧15°. 
     
     
         6 . The nanostructured titanium alloy article according to  claim 1 , wherein ≧80% of the grains have a grain shape aspect ratio that is in a range of 0.3 to 0.7. 
     
     
         7 . The nanostructured titanium alloy article according to  claim 1 , wherein the developed titanium structure is processed from a combination of a severe plastic deformation process type and non-severe plastic deformation type thermomechanical processing steps. 
     
     
         8 . The nanostructured titanium alloy article according to  claim 1 , wherein the developed titanium structure has an average crystallite size is ≦100 nanometers. 
     
     
         9 . The nanostructured titanium alloy article according to  claim 8 , wherein the developed titanium structure has a dislocation density is ≧10 15  m −2 . 
     
     
         10 . The nanostructured titanium alloy article according to  claim 9 , wherein 20-40% of the grains have high angle grain boundaries with a misorientation angle ≧15°. 
     
     
         11 . The nanostructured titanium alloy article according to  claim 10 , wherein ≧80% of the grains have a grain shape aspect ratio in a range from 0.3 to 0.7. 
     
     
         12 . The nanostructured titanium alloy article according to  claim 11 , wherein the developed titanium structure has an ultimate tensile strength ≧1200 MPa. 
     
     
         13 . The nanostructured titanium alloy article according to  claim 12 , wherein the ultimate tensile strength ≧1400 MPa. 
     
     
         14 . The nanostructured titanium alloy article according to  claim 12 , wherein the developed titanium structure has a total tensile elongation ≧10%. 
     
     
         15 . The nanostructured titanium alloy article according to  claim 14 , wherein the developed titanium structure has an area reduction ≧25%. 
     
     
         16 . The nanostructured titanium alloy article according to  claim 15 , wherein the developed titanium structure has an ultimate shear strength is ≧650 MPa. 
     
     
         17 . The nanostructured titanium alloy article according to  claim 16 , wherein the ultimate shear strength ≧740 MPa. 
     
     
         18 . The nanostructured titanium alloy article according to  claim 16 , wherein the developed titanium structure has an axial fatigue endurance limit ≧700 MPa measured at 10 7  cycles. 
     
     
         19 . The nanostructured titanium alloy article according to  claim 18 , wherein the axial fatigue endurance limit ≧950 MPa measured at 10 7  cycles. 
     
     
         20 . The nanostructured titanium alloy article according to  claim 18 , wherein the developed titanium structure has a cantilever-rotating beam fatigue endurance limit ≧650 MPa measured at 10 7  cycles. 
     
     
         21 . The nanostructured titanium alloy article according to  claim 20 , wherein the cantilever-rotating beam fatigue endurance limit ≧700 MPa measured at 10 7  cycles. 
     
     
         22 . The nanostructured titanium alloy article according to  claim 1 ,
 wherein the developed titanium structure includes α-titanium matrix having retained β-titanium particles.   
     
     
         23 . The nanostructured titanium alloy article according to  claim 1 , wherein the developed titanium structure has a composition by weight percent:
 nitrogen (N) 0.07% maximum;   carbon (C) 0.1% maximum;   hydrogen (H) 0.015% maximum;   iron (Fe) 0.50% maximum;   oxygen (O) 0.40% maximum;   trace impurities 0.40% maximum; and   a balance of titanium (Ti).   
     
     
         24 . The nanostructured titanium alloy article according to  claim 23 , wherein the developed titanium structure has a composition by weight percent:
 Aluminum (Al) 6.75% maximum; and   Vanadium (V) 4.5% maximum.   
     
     
         25 . The nanostructured titanium alloy article according to  claim 23 , wherein the developed titanium structure has a composition by weight percent:
 Aluminum (Al) 6.5% maximum;   Niobium (Nb) 7.5% maximum; and   Tantalum (Ta) 0.5% maximum.   
     
     
         26 . The nanostructured titanium alloy article according to  claim 23 , wherein the developed titanium structure has a composition by weight percent:
 Zirconium (Zr) 25% maximum; and   other elements 1% maximum.   
     
     
         27 . A method for making a nanostructured titanium alloy, comprising the steps of:
 providing a workpiece of a titanium alloy;   inducing severe plastic deformation to the workpiece using an equal-channel angular pressing-conform machine at temperatures ≦650° C. and having a die set at a channel angle of intersection between ψ=75° and ψ=135°; and   subjecting the workpiece to thermomechanical processing at temperatures ≦550° C. to prepare an article having a cross-sectional area reduction ≧35%.