Titanium alloy-based sheet material for low-temperature superplastic deformation

Abstract

Herein disclosed includes the manufacture of sheets from a titanium alloy having a chemical composition efficiently balanced with manufacturability based on known conventional manufacturing techniques for finished products exhibiting low temperature superplastic forming properties. The result is achieved by a sheet material for low temperature superplastic made of titanium alloy with the following content of element by % wt.: 4.5-5.5Al, 4.5-5.5V, 0.1-1.0Mo, 0.8-1.5Fe, 0.1-0.5Cr, 0.1-0.5Ni, 0.16-0.25O, remainder is titanium and residual elements and having molybdenum structural equivalent [Mo]eqiv.>5 and aluminum structural equivalent [Al]equiv.<8; the equivalent values are calculated from the expressions: [Mo]eqiv.=[Mo]+[V]/1.5+[Cr]×1.25+[Fe]×2.5+[Ni]/0.8 [Al]eqiv.=[Al]+[O]×10+[Zr]/6.

1 - 5 . (canceled) 
     
     
         6 . Sheet material for low temperature superplastic forming made of titanium alloy with the following content of element by % wt.: 4.5-5.5Al, 4.5-5.5V, 0.1-1.0Mo, 0.8-1.5Fe, 0.1-0.5Cr, 0.1-0.5Ni, 0.16-0.25O, remainder is titanium and residual elements, having molybdenum structural equivalent [Mo]eqiv.>5 and aluminum structural equivalent [Al]equiv.<8; the equivalent values are calculated from the expressions:
   [Mo]eqiv.=[Mo]+[V]/1.5+[Cr]×1.25+[Fe]×2.5+[Ni]/0.8
     [Al]eqiv.=[Al]+[O]×10+[Zr]/6.
   
     
     
         7 . Sheet material for low temperature superplastic forming of claim  1  with the structure consisting of grains with the size below 8 μm. 
     
     
         8 . Sheet material for low temperature superplastic forming of claim  1  exhibiting superplastic properties at a temperature of 775±10° C. 
     
     
         9 . Sheet material for low temperature superplastic forming of claim  1  exhibiting at a temperature of 775±10° C. α/β phase ratio from 0.9 to 1.1. 
     
     
         10 . Sheet material for low temperature superplastic forming of claim  1  with the amount of alloying elements diffusible between α- and β-phases during SPF process equal to 0.5% minimum and which is determined from the following relation:
 where:
     Q=Σ   j=1   n   |Δm|≥ 0.5% wt. 
 
 Q—amount of diffusible alloying elements in the material during SPF, % wt., 
 n—amount of alloying elements in the material, 
 |Δm|—absolute variation value of alloying element content in β- and α-phases, % wt. during SPF process, 
 |Δm|—is calculated from the formula:
   |Δ m |=( mβ 1− mα 1)−( mβ 2− mα 2), % wt.
 
 
 
       where:
 mβ1—content of alloying element in β-phase before SPF, % wt., 
 mβ2—content of alloying element in β-phase after SPF, % wt., 
 mα1—content of alloying element in α-phase before SPF, % wt., 
 mα2—content of alloying element in α-phase after SPF, % wt. 
 
     
     
         11 . Sheet material for low temperature superplastic forming of claim  1 , wherein iron is present in an amount of 1.0% to 1.5%. 
     
     
         12 . Sheet material for low temperature superplastic forming of claim  1 , wherein said sheet material has a thickness of about 2 mm. 
     
     
         13 . Sheet material for low temperature superplastic forming of claim  1 , wherein said sheet material is used to make a semi-finished aerospace product having grain size over 2 μm. 
     
     
         14 . Sheet material for low temperature superplastic forming of claim  1 , wherein said sheet material is in the form of a bar, tube, section, open- and close-dye forging, plate, sheet, strip or foil. 
     
     
         15 . Sheet material for low temperature superplastic forming of claim  1 , wherein said sheet material is used in a structure used in one of an airborne vehicle, a rocket or a medical implant.