Processing for titanium alloys
AssigneeUnited Technologies Corporation
InventorsDouglas M. Berczik, George Brodi, Thomas E. O'Connell
Life of this patent
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Abstract
Process for improving the crack growth behavior of titanium alloys containing substantial beta stabilizers and at least 3% molybdenum, such as Ti-6-2-4-6. The process includes the steps of forging above the beta transus temperature, cooling at a controlled rate through the beta transus temperature, heating to a temperature between 50.degree.-150.degree. F. below the beta transus temperature, cooling the alloy at a rate in excess of that produced by air cooling, and aging the material between about 900.degree. F. and 1100.degree. F. The resultant material has substantially improved crack growth behavior when contrasted with material processed according to the prior art.
Claims11
Method for improving the crack growth behavior of alpha-beta titanium material containing substantial amounts of beta stabilizers and at least 3% Mo, and having a beta transus temperature, including the steps of
- a. forging the material above the beta transus an amount sufficient to produce recrystallization
- b. cooling the material, through the beta transus, at a rate of from about 20.degree. to about 100.degree. F. per minute
- c. heat treating the material at a temperature between about 50.degree. and about 150.degree. F. below the beta transus
- d. cooling the alloy at a rate equal to or in excess of that produced by air cooling
- e. aging the material.
Method for thermomechanically processing titanium alloy articles (nominal composition 6% Al, 2% Sn, 4% Zr, 6% Mo, balance essentially Ti) including the steps of
- a. forging the material an amount equivalent to at least a 10% reduction area at a temperature between about 25% and about 65% above the gamma prime solvus
- b. cooling the material to below about 1000.degree. F. at a rate between about 20.degree. and above 100.degree. F. per minute
- c. heat treating the material at a temperature between about 50.degree. F. and 150.degree. F. below the gamma prime solvus for about 0.5-5 hours
- d. cooling the material to below about 500.degree. F. at a rate equal or in excess of that produced by air cooling
- e. aging the material for about 2-10 hours at a temperature between about 900.degree. F. and about 1200.degree. F.
A titanium alloy article resistant to crack growth which comprises:
- a. a beta matrix containing
- b. from about 20 to about 90 volume percent alpha platelets having an average 1/d of between about 4 and about 20
- c. said needles being surrounded by a thin layer having a high Mo content
- d. said material being substantially free of any continuous grain boundary alpha phase.
Dependencies are inferred from the claim text.