Thermomechanical processing of alpha-beta titanium alloys

• US 10,370,751 B2
• Filed: 07/26/2017
• Issued: 08/06/2019
• Est. Priority Date: 03/15/2013
• Status: Active Grant

• Current Assignee: ATI Properties LLC (CNH Industrial N.V.)
• Original Assignee: ATI Properties LLC (CNH Industrial N.V.)
• Inventors: Thomas, Jean-Phillippe A., Minisandram, Ramesh S., Forbes Jones, Robin M., Mantione, John V., Bryan, David J.
• Primary Examiner(s): Yang, Jie
• Application Number:
  US15/659,661
• Publication Number:
  US 20170321313A1
• Time in Patent Office: 741 Days
• Field of Search: 148670
• CPC Class Codes: C22C 14/00 Alloys based on titanium
• CPC Class Codes: C22F 1/183 of titanium or alloys based thereon

Abstract

One embodiment of a method of refining alpha-phase grain size in an alpha-beta titanium alloy comprises working an alpha-beta titanium alloy at a first working temperature within a first temperature range in the alpha-beta phase field of the alpha-beta titanium alloy. The alloy is slow cooled from the first working temperature. On completion of working at and slow cooling from the first working temperature, the alloy comprises a primary globularized alpha-phase particle microstructure. The alloy is worked at a second working temperature within a second temperature range in the alpha-beta phase field. The second working temperature is lower than the first working temperature. The is worked at a third working temperature in a third temperature range in the alpha-beta phase field. The third working temperature is lower than the second working temperature. After working at the third working temperature, the titanium alloy comprises a desired refined alpha-phase grain size.

Claims

1. A method of refining alpha-phase grain size in an alpha-beta titanium alloy workpiece, the method comprising:

forging an alpha-beta titanium alloy at a first forging temperature within a first forging temperature range,

wherein forging the alpha-beta titanium alloy at the first forging temperature comprises at least one pass of both upset forging and draw forging, and

wherein the first forging temperature range spans 300°

F. below the beta transus up to a temperature 30°

F. below a beta transus temperature of the alpha-beta titanium alloy;

slow cooling the alpha-beta titanium alloy from the first forging temperature, wherein the step of slow cooling comprises cooling the alpha-beta titanium alloy at a cooling rate no greater than 5°

F. per minute;

forging the alpha-beta titanium alloy at a second forging temperature within a second forging temperature range,

wherein forging the alpha-beta titanium alloy at the second forging temperature comprises at least one pass of both upset forging and draw forging,

wherein the second forging temperature range comprises a temperature range spanning 600°

F. to 350°

F. below the beta transus, and

wherein the second forging temperature is lower than the first forging temperature; and

forging the alpha-beta titanium alloy at a third forging temperature within a third forging temperature range,

wherein forging the alpha-beta titanium alloy at the third forging temperature comprises radial forging,

wherein the third forging temperature range is 1000°

F. to 1400°

F., and

wherein the third forging temperature is lower than the second forging temperature.

2. The method according to claim 1, wherein the alpha-beta titanium alloy is one of a Ti-6Al-4V alloy (UNS R56400), a Ti-6Al-4V ELI alloy (UNS R56401), a Ti-6Al-2Sn-4Zr-2Mo alloy (UNS R54620), a Ti-6Al-2Sn-4Zr-6Mo alloy (UNS R56260), and a Ti-4Al-2.5V-1.5Fe alloy (UNS 54250).

3. The method according to claim 1, wherein the alpha-beta titanium alloy is one of a Ti-6Al-4V alloy (UNS R56400) and a Ti-6Al-4V ELI alloy (UNS R56401).

4. The method according to claim 1, wherein the alpha-beta titanium alloy is a Ti-4Al-2.5V-1.5Fe alloy (UNS 54250).

5. The method according to claim 1, wherein the slow cooling comprises furnace cooling.

6. The method according to claim 1, wherein slow cooling comprises transferring the alpha-beta titanium alloy from a furnace set at the first forging temperature to a furnace set at the second forging temperature.

7. The method according to claim 1, further comprising, after the step of slow cooling the alpha-beta titanium alloy from the first forging temperature, heat treating the alpha-beta titanium alloy at a heat treating temperature in the first forging temperature range, and holding the alpha-beta titanium alloy at the heat treating temperature.

8. The method according to claim 7, wherein holding the alpha-beta titanium alloy at the heat treating temperature comprises holding the alpha-beta titanium alloy at the heat treating temperature for a heat treating time in a time range from 1 hour to 48 hours.

9. The method according to claim 1, further comprising annealing the alpha-beta titanium alloy after forging at the second forging temperature.

10. The method according to claim 9, wherein annealing comprises heating the alpha-beta titanium alloy to an annealing temperature in an annealing temperature range spanning 500°

F. to 250°

F. below the beta transus and for 30 minutes to 12 hours.

11. The method according to claim 1, further comprising reheating the alpha-beta titanium alloy intermediate any of the at least one or more press forging steps.

12. The method according to claim 11, wherein reheating comprises heating the alpha-beta titanium alloy back to a previous working temperature, and holding the alpha-beta titanium alloy at the previous working temperature for a reheating time in a range spanning 30 minutes to 6 hours.

13. The method according to claim 1, wherein radial forging comprises one series of at least two and no more than six reductions, wherein the radial forging temperature range is 1100°

F. to 1400°

F.

14. The method according to claim 1, wherein radial forging comprises a multiple series of at least two and no more than six reductions at radial forging temperatures starting at no more than 1400°

F. and decreasing to no less than 1000°

F., with a reheat step prior to each reduction.

15. The method according to claim 1, further comprising:

prior to forging the titanium alloy at the first forging temperature, beta heat treating the alpha-beta titanium alloy at a beta heat treating temperature,

wherein the beta heat treating temperature is from a beta transus temperature of the alpha-beta titanium alloy to a temperature 300°

F. greater than the beta transus temperature of the alpha-beta titanium alloy; and

quenching the alpha-beta titanium alloy.

16. The method according to claim 15, wherein beta heat treating the alpha-beta titanium alloy further comprises working the alpha-beta titanium alloy at the beta heat treating temperature.

17. The method according to claim 16, wherein working the alpha-beta titanium alloy at the beta heat treating temperature comprises one or more of roll forging, swaging, cogging, open-die forging, impression-die forging, press forging, automatic hot forging, radial forging, upset forging, draw forging, and multiaxis forging.