Alloy and method of treating titanium aluminide

• US 20080041506A1
• Filed: 08/17/2007
• Published: 02/21/2008
• Est. Priority Date: 08/19/2006
• Status: Abandoned Application

• Current Assignee: Rolls-Royce PLC (Rolls-Royce Holdings Plc)
• Original Assignee: Rolls-Royce PLC (Rolls-Royce Holdings Plc)
• Inventors: Huang, Aijun, Wu, Xinhua, Loretto, Michael, Hu, Dawei
• Application Number:
  US11/889,917
• Publication Number:
  US 20080041506A1
• Time in Patent Office: Days
• US Class Current: 148/669
• CPC Class Codes: C22C 14/00 Alloys based on titanium
• CPC Class Codes: C22C 21/00 Alloys based on aluminium
• CPC Class Codes: C22F 1/04 of aluminium or alloys based thereon
• CPC Class Codes: C22F 1/183 of titanium or alloys based thereon
• CPC Class Codes: F04D 29/002 especially adapted for elastic fluid pumps

Abstract

A method of treating a titanium aluminide alloy having a single alpha phase field and being capable of producing a massively transformed gamma microstructure by subjecting the alloy to a temperature cycle that produces the massively transformed microstructure having a refined microstructure; the method being characterised in that oxygen securing means are provided within the alloy to prevent diffusion of oxygen to the grain boundary.

Claims

1. A method of enhancing massive transformation of a titanium aluminide alloy having a single alpha phase field by incorporating up to 0.5 at % of oxygen scouring means into the alloy which inhibits diffusion of oxygen within the alpha phase field to the grain boundary as the alloy is subjected to a temperature cycle which produces a massively transformed gamma microstructure.

2. A method according to claim 1, wherein the oxygen scouring means is incorporated up to 0.2 at %.

3. A method according to claim 1, wherein the temperature cycle comprises the steps a) heating the titanium aluminide alloy to a temperature above the alpha transus temperature, b) maintaining the titanium aluminide alloy at a temperature above the alpha transus temperature for a predetermined time period, c) cooling the titanium aluminide alloy from the single alpha phase field to produce a massively transformed gamma microstructure.

4. A method according to claim 3, wherein the heat treatment further comprises the step of d) heating the titanium aluminide to a temperature below the alpha transus temperature in the alpha and gamma phase field, e) maintaining the titanium aluminide at the temperature below the alpha transus temperature for a predetermined time period to precipitate alpha plates in the massively transformed gamma microstructure such that a refined microstructure is produced, and f) cooling the titanium aluminide to ambient temperature.

5. A method according to claim 1, wherein the oxygen securing means is selected from the group comprising yttrium and hafnium.

6. A method according to claim 1, wherein the alloy consists at least 43 at % aluminium, 0 to 9 at % niobium, 0 to 10 at % tantalum, 0.01 to 0.15 at % yttrium, the balance being titanium plus incidental impurities.

7. A method according to claim 1, wherein step c) comprises cooling the titanium aluminide to ambient temperature.

8. A method according to claim 1, wherein the titanium aluminide is cooled by gas cooling, oil cooling, fluidised bed cooling or salt cooling.

9. A method according to claim 1, wherein step c) comprises cooling the titanium aluminide at a cooling rate of 4°

C.S<sup>−

1</sup> to 150°

C.S<sup>−

1</sup>.

10. A method as claimed in claim 1, wherein the titanium aluminide alloy is a cast titanium aluminide component.

11. A method as claimed in claim 10, wherein the method further comprises the step of hot isostatic pressing the cast titanium aluminide component.

12. A method as claimed in claim 1, wherein the titanium aluminide alloy provides a compressor blade or a compressor vane.

13. An alloy consisting of 43 to 50 at % aluminium, 0 to 9 at % niobium, 0 to 10 at % tantalum, 0.01 to 0.2 at % of yttrium and/or hafnium, the balance being titanium plus incidental impurities.

14. An alloy according to claim 13, consisting of 45 to 46 at % aluminium, 7 to 9 at % niobium, 0.02 to 0.15 at % yttrium, the balance being titanium plus incidental impurities.

15. An alloy according to claim 13, wherein the niobium plus tantalum is less than or equal to 10 at %.

16. An alloy claimed in claim 13, wherein the titanium aluminide alloy is a cast titanium aluminide component.