Metastable beta-titanium alloys and methods of processing the same by direct aging

• US 20050257864A1
• Filed: 02/14/2005
• Published: 11/24/2005
• Est. Priority Date: 05/21/2004
• Status: Active Grant

• Current Assignee: ATI Properties LLC
• Original Assignee: ATI Properties Incorporated (Allegheny Technologies Incorporated)
• Inventors: Freese, Howard L., Jablokov, Victor R., Marquardt, Brian, Wood, John Randolph
• Granted Patent: US 7,837,812 B2
• Time in Patent Office: Days
• US Class Current: 148/671
• CPC Class Codes: C22C 14/00 Alloys based on titanium
• CPC Class Codes: C22F 1/183 of titanium or alloys based thereon

Abstract

Metastable beta titanium alloys and methods of processing metastable β-titanium alloys are disclosed. For example, certain non-limiting embodiments relate to metastable β-titanium alloys, such as binary β-titanium alloys comprising greater than 10 weight percent molybdenum, having tensile strengths of at least 150 ksi and elongations of at least 12 percent. Other non-limiting embodiments relate to methods of processing metastable β-titanium alloys, and more specifically, methods of processing binary β-titanium alloys comprising greater than 10 weight percent molybdenum, wherein the method comprises hot working and direct aging the metastable β-titanium alloy at a temperature below the β-transus temperature of the metastable β-titanium alloy for a time sufficient to form α-phase precipitates in the metastable β-titanium alloy. Articles of manufacture comprising binary β-titanium alloys according to various non-limiting embodiments disclosed herein are also disclosed.

Claims

1. A method of processing a metastable β

-titanium alloy comprising greater than 10 weight percent molybdenum, the method comprising;

hot working the metastable β

-titanium alloy; and

direct aging the metastable β

-titanium alloy, wherein direct aging comprises heating the metastable β

-titanium alloy in the hot worked condition at an aging temperature ranging from 850°

F. to 1375°

F. for a time sufficient to form α

-phase precipitates within the metastable β

-titanium alloy.

2. The method of claim 1 wherein the metastable β

-titanium alloy is a binary titanium-molybdenum alloy comprising from 14 weight percent to 16 weight percent molybdenum.

3. The method of claim 1 wherein hot working the metastable β

-titanium alloy comprises one of;

hot rolling the metastable β

-titanium alloy at a roll temperature ranging from greater than 1100°

F. to 1725°

F. and hot extruding the metastable β

-titanium alloy at a temperature ranging from 1000°

F. to 2000°

F.

4. The method of claim 1 wherein the metastable β

-titanium alloy is hot worked to a percent reduction in area ranging from 95% to 99%.

5. The method of claim 1 wherein the aging temperature ranges from greater than 900°

F. to 1200°

F.

6. The method of claim 1 wherein the aging temperature ranges from 925°

F. to 1150°

F.

7. The method of claim 1 wherein the aging temperature ranges from 950°

F. to 1100°

F.

8. The method of claim 1 wherein prior to hot working the metastable β

-titanium alloy, the metastable β

-titanium alloy is produced by a process comprising at least one of plasma arc cold hearth melting and vacuum arc remelting.

9. The method of claim 1 wherein after processing, the metastable β

-titanium alloy has a tensile strength of at least 150 ksi.

10. The method of claim 1 wherein after processing, the metastable β

-titanium alloy has a tensile strength of at least 170 ksi.

11. The method of claim 1 wherein after processing, the metastable β

-titanium alloy has a tensile strength of at least 180 ksi.

12. The method of claim 1 wherein after processing, the metastable β

-titanium alloy has an elongation of at least 12 percent.

13. The method of claim 1 wherein after processing, the metastable β

-titanium alloy has an elongation of at least 15 percent.

14. The method of claim 1 wherein after processing, the metastable β

-titanium alloy has an elongation of at least 20 percent.

15. A method of processing a metastable β

-titanium alloy comprising greater than 10 weight percent molybdenum, the method comprising;

hot working a metastable β

-titanium alloy; and

direct aging the metastable β

-titanium alloy, wherein direct aging comprises;

heating the metastable β

-titanium alloy in the hot worked condition at a first aging temperature below the β

-transus temperature of the metastable β

-titanium alloy for a time sufficient to form and at least partially coarsen at least one α

-phase precipitate within at least a portion of the metastable β

-titanium alloy; and

subsequently

heating the metastable β

-titanium alloy at a second aging temperature that is lower than the first aging temperature for a time sufficient to form at least one additional α

-phase precipitate within at least a portion of the metastable β

-titanium alloy.

16. The method of claim 15 wherein the metastable β

-titanium alloy is a binary titanium-molybdenum alloy comprising from 14 weight percent to 16 weight percent molybdenum.

17. The method of claim 15 wherein hot working the metastable β

-titanium alloy comprises one of;

hot rolling the metastable β

-titanium alloy at a roll temperature ranging from greater than 1100°

F. to 1725°

F. and hot extruding the metastable β

-titanium alloy at a temperature ranging from 1000°

F. to 2000°

F.

18. The method of claim 15 wherein the metastable β

-titanium alloy is hot worked to a reduction in area of ranging from 95% to 99%.

19. The method of claim 15 wherein the first aging temperature ranges from 1225°

F. to 1375°

F.

20. The method of claim 15 wherein the first aging temperature ranges from 1250°

F. to 1350°

F.

21. The method of claim 15 wherein the first aging temperature ranges from 1275°

F. to 1325°

F.

22. The method of claim 15 wherein the first aging temperature ranges from 1275°

F. to 1300°

F.

23. The method of claim 15 wherein the second aging temperature ranges from 850°

F. to 1000°

F.

24. The method of claim 15 wherein the second aging temperature ranges from 875°

F. to 1000°

F.

25. The method of claim 15 wherein the second aging temperature ranges from 900°

F. to 1000°

F.

26. The method of claim 15 wherein prior to direct aging the metastable β

-titanium alloy has a microstructure comprising metastable phase regions, and

heating the metastable β

-titanium alloy at the first aging temperature comprises heating the metastable β

-titanium alloy for a time sufficient to form and at least partially coarsen α

-phases precipitate within at least a portion of the metastable phase regions; and

heating the metastable β

-titanium alloy at a second aging temperature comprises heating the metastable β

-titanium alloy for a time sufficient to form α

-phase precipitates within a majority of remaining metastable phase regions in the metastable β

-titanium alloy.

27. The method of claim 26 wherein heating the metastable β

-titanium alloy at a second aging temperature comprises heating the metastable β

-titanium alloy for a time sufficient to form α

-phase precipitates within essentially all of the remaining metastable phase regions in the metastable β

-titanium alloy.

28. The method of claim 15 wherein after processing, the metastable β

-titanium alloy has a microstructure comprising at least one coarse α

-phase precipitate and at least one fine α

-phase precipitate.

29. The method of claim 15 wherein after processing, the metastable β

-titanium alloy has a tensile strength of at least 150 ksi.

30. The method of claim 15 wherein after processing, the metastable β

-titanium alloy has a tensile strength of at least 170 ksi.

31. The method of claim 15 wherein after processing, the metastable β

-titanium alloy has a tensile strength of at least 180 ksi.

32. The method of claim 15 wherein after processing, the metastable β

-titanium alloy has an elongation of at least 12 percent.

33. The method of claim 15 wherein after processing, the metastable β

-titanium alloy has an elongation of at least 15 percent.

34. The method of claim 15 wherein after processing, the metastable β

-titanium alloy has an elongation of at least 20 percent.

35. The method of claim 15 wherein after processing, the binary β

-titanium alloy has a rotating beam fatigue strength of at least 550 MPa.

36. The method of claim 15 wherein after processing, the binary β

-titanium alloy has a rotating beam fatigue strength of at least 650 MPa.

37. The method of claim 15 wherein prior to hot working the metastable β

-titanium alloy, the metastable β

-titanium alloy is produced by a process comprising at least one of plasma arc cold hearth melting and vacuum arc remelting.

38. A method of processing a metastable β

-titanium alloy comprising greater than 10 weight percent molybdenum, the method comprising;

hot working a metastable β

-titanium alloy; and

direct aging the metastable β

-titanium alloy, wherein direct aging comprises;

heating the metastable β

-titanium alloy in the hot worked condition at a first aging temperature ranging from 1225°

F. to 1375°

F. for at least 0.5 hours; and

subsequently

heating the metastable β

-titanium alloy at a second aging temperature ranging from 850°

F. to 1000°

F. for at least 0.5 hours.

39. A method of processing a metastable β

-titanium alloy comprising greater than 10 weight percent molybdenum, the method comprising;

hot working the metastable β

-titanium alloy to a reduction in area of at least 95 percent by at least one of hot rolling and hot extruding the metastable β

-titanium alloy; and

direct aging the metastable β

-titanium alloy by heating the metastable β

-titanium alloy in the hot worked condition at an aging temperature below the β

-transus temperature of metastable β

-titanium alloy for a time sufficient to form α

-phase precipitates within the metastable β

-titanium alloy.

40. A method of processing a binary β

-titanium alloy comprising greater than 10 weight percent molybdenum, the method comprising;

hot working the binary β

-titanium alloy; and

direct aging the binary β

-titanium alloy by heating the β

-titanium alloy in the hot worked condition at an aging temperature below the β

-transus temperature of the binary β

-titanium alloy for a time sufficient to form α

-phase precipitates within the binary β

-titanium alloy;

wherein after processing, the binary β

-titanium alloy has a tensile strength of at least 150 ksi and an elongation of at least 12 percent.

41. The method of claim 40 wherein direct aging the binary β

-titanium alloy comprises one of a single-step direct aging process and a two-step direct aging process.

42. The method claim 40 wherein after processing, the binary β

-titanium alloy has a tensile strength ranging from 150 ksi to 180 ksi and an elongation ranging from 12 percent to 20 percent.

43. A binary β

-titanium alloy comprising greater than 10 weight percent molybdenum and having a tensile strength of at least 150 ksi and an elongation of at least 12 percent.

44. The binary β

-titanium alloy of claim 43 wherein the binary β

-titanium alloy has an elongation of at least 20 percent.

45. The binary β

-titanium alloy of claim 43 wherein the binary β

-titanium alloy has a tensile strength ranging from 150 ksi to 180 ksi and an elongation ranging from 12 percent to 20 percent.

46. The binary β

-titanium alloy of claim 43 wherein the binary β

-titanium alloy has a rotating beam fatigue strength of at least 650 MPa.

47. An article of manufacture comprising a binary β

-titanium alloy according to claim 43.

48. The article of manufacture of claim 43 wherein the article of manufacture is selected from the group consisting of biomedical components;

automotive components;

aerospace components;

chemical processing components; and

nautical components.

49. The article of manufacture of claim 48 wherein biomedical components are selected from the group consisting of hip stems, femoral heads, bone screws, cannulated screws, tibial trays, dental implants, intermedullary nails, valve lifters, retainers, tie rods, suspension springs, fasteners, screws, valve bodies, pump casings, pump impellers, vessels, pipe flanges, fasteners, screws, hatch covers, clips, connectors, ladders, handrails, wires, and cables.