Powder metallurgy methods for the production of fine and ultrafine grain Ti and Ti alloys

Patent metadata

Field	Value
Publication number	US-9816157-B2
Application number	US-201414152787-A
Country	US
Kind code	B2
Filing date	Jan 10, 2014
Priority date	Apr 26, 2011
Publication date	Nov 14, 2017
Grant date	Nov 14, 2017

Abstract

A process includes sintering hydrogenated titanium or titanium hydride (TiH 2 ) and/or Ti metal in a dynamically controlled hydrogen atmosphere with hydrogen partial pressure greater than 0.01 atmosphere and at elevated temperature, to form a sintered titanium material; equilibrate the sintered material at an equilibration temperature below the sintering temperature and above the phase transformations including eutectoid decomposition temperature for an equilibration time sufficient for the hydrogen within the sample to reach equilibrium and homogenize the sintered titanium material; holding the sintered titanium material at a hold temperature below the temperature of sintering and a hold time sufficient for phase transformations including eutectoid decomposition of the sintered titanium material; and heating the sintered titanium material under vacuum, inert atmosphere, or a combination of both at a hold temperature which is less than that of the sintering temperature, to form titanium metal, or a titanium metal alloy with fine or ultrafine grain sizes; where the dynamically controlled hydrogen atmosphere varies as a function of time and temperature throughout the thermal cycle and includes hydrogen during the sintering and phase transformations including eutectoid decomposition steps.

First claim

What is claimed is:

1. A process for producing a sintered titanium material with fine grain size comprising:
sintering a particulate titanium feed material in a dynamically controlled hydrogen atmosphere at an elevated temperature to form a sintered titanium material containing hydrogen, wherein the particulate titanium feed material includes at least one of titanium metal (Ti) and hydrogenated titanium or Ti hydride (TiH 2 ), wherein the dynamically controlled hydrogen atmosphere comprises primarily hydrogen that was not produced from the particulate titanium feed material, and wherein the sintered titanium material has a density greater than 95%; and
heating the sintered titanium material under vacuum or controlled inert atmosphere at a temperature which is less than the sintering temperature sufficient to remove hydrogen from the sintered titanium material.

2. The process of claim 1 , further comprising equilibrating the sintered material at an equilibration temperature below the sintering temperature and above the temperature of phase transformations including eutectoid decomposition for an equilibration time sufficient for the hydrogen within the sample to reach equilibrium with the dynamically controlled hydrogen atmosphere and homogenize the sintered titanium material.

3. The process of claim 1 , further comprising holding the sintered titanium material at a hold temperature below the said elevated temperature of sintering and a hold time sufficient for phase transformations including eutectoid decomposition of the sintered titanium material.

4. The process of claim 3 , wherein the holding is performed in the dynamically controlled hydrogen atmosphere.

5. The process of claim 3 , wherein the phase transformations hold temperature is from about 400° C. to about 800° C.

6. The process of claim 3 , wherein the phase transformations hold temperature is from about 150° C. to about 400° C.

7. The process of claim 3 , wherein the phase transformations hold time is from about 10 minutes to about 120 hours.

8. The process of claim 1 , wherein the sintering further comprises sintering the particulate titanium feed material in the presence of an alloying additive.

9. The process of claim 1 , wherein the dynamically controlled hydrogen atmosphere includes a mixture of the hydrogen and an inert gas.

10. The process of claim 1 , wherein the dynamically controlled hydrogen atmosphere consists essentially of hydrogen at a controlled absolute pressure.

11. The process of claim 1 , wherein the sintered titanium material has a microstructure comprising α-phase, α2-phase, δ-phase and β phase.

12. The process of claim 1 , wherein the elevated temperature is from about 1000° C. to about 1500° C.

13. The process of claim 1 , wherein the dynamically controlled hydrogen atmosphere includes a partial pressure of hydrogen, and the partial pressure of hydrogen and the elevated temperature are sufficient to form a solid solution of β-phase titanium with hydrogen.

14. The process of claim 13 , wherein the partial pressure of hydrogen is greater than 0.01 atm.

15. The process of claim 1 , wherein the sintering is conducted from about 5 minutes to about 30 hours.

16. The process of claim 1 , wherein heating the sintered titanium material under vacuum or controlled inert atmosphere is conducted from about 400° C. to about 900° C.

17. The process of claim 1 , wherein heating the sintered titanium material under vacuum or controlled inert atmosphere is conducted from about 1 hour to about 200 hours.

18. The process of claim 1 , wherein the sintered titanium material has a final grain size of from about 10 nm to about 10 μm.

19. The process of claim 1 , wherein the sintered titanium material has a final grain size of from about 10 μm to about 100 μm.

20. The process of claim 1 , wherein the dynamically controlled hydrogen atmosphere has a hydrogen to inert gas ratio from about 1:100 to about 1:0.

21. The process of claim 1 , wherein the dynamically controlled hydrogen atmosphere has an absolute pressure of 0.01 atm to 10 atm.

22. The process of claim 1 , wherein the dynamically controlled hydrogen atmosphere includes a hydrogen partial pressure which is varied during the process in order to achieve a target hydrogen concentration within the sintered titanium material as a function of time.

23. The process of claim 1 , further comprising cooling the sintered titanium material at a non-uniform rate, wherein the cooling is at least one of cooling from the elevated temperature to the equilibration temperature and cooling from the equilibration temperature to the phase transformations including eutectoid decomposition temperature.

24. The process of claim 1 , wherein the sintered titanium material has a density of greater than 99%.

25. The process of claim 1 , wherein the as-sintered titanium material has an average grain size less than 20 micrometer.

26. The process of claim 1 , wherein the as-sintered titanium material has an average grain size less than 5 micrometer.

27. The process of claim 1 , wherein the sintered titanium material has an oxygen content of from about 0.001 wt % to about 0.5 wt %.

28. The process of claim 1 , wherein the particulate titanium feed material comprises a powder having an initial size from about 20 mesh to about 1200 mesh.

29. The process of claim 1 , wherein the particulate titanium feed material comprises a powder having an average initial size from about 325 to about 400 mesh.

30. The process of claim 1 , wherein the particulate titanium feed material comprises a powder having an initial size from about 400 to about 1200 mesh.

31. The process of claim 1 , wherein the particulate titanium feed material is prepared by combining source powders having average particle sizes greater than 20 μm with a non-volatile liquid to produce a mixture, and subjecting the mixture to a particle size reduction process such that the particulate titanium feed material has average particle sizes less than 20 μm.

32. The process claim 1 , which is void of post-sintering mechanical processing steps.

33. The process of claim 1 , wherein the sintered titanium material has a density of greater than 97%.

Assignees

• Univ Utah Res Found

Inventors

• Fang Zhigang Zak
• Sun Pei
• Paramore James
• Wang Hongtao
• Koopman Mark
• Yang Lu

Classifications

• C22C1/0458 Primary

  Alloys based on titanium, zirconium or hafnium · CPC title

• B22F2999/00

  Aspects linked to processes or compositions used in powder metallurgy · CPC title

• B22F2201/20

  Use of vacuum · CPC title

• B22F3/101

  Changing atmosphere · CPC title

• B22F2201/013

  Hydrogen · CPC title