Method to prevent abnormal grain growth for beta annealed Ti—6AL—4V forgings
A method for heat-treating a titanium alloy, such as Ti-6Al-4V. The method may occur after or include a step of forging the titanium alloy such that localized, highly deformed grains are formed in the titanium alloy. Then the method may include steps of recrystallization annealing the titanium alloy by heating the titanium alloy to a temperature in a range between 30° F. to 200° F. below beta transus of the titanium alloy for 1 hour to 6 hours and then furnace cooling of the titanium alloy to 1200° F. to 1500° F. at a rate of 50° F. to 500° F. per hour. Following the recrystallization annealing, the method may include beta annealing the titanium alloy. These steps may be performed in a single heat treating cycle.
1. A method for heat-treating a titanium alloy, the method comprising the steps of:
recrystallization annealing the titanium alloy, wherein recrystallization annealing includes heating the titanium alloy to a temperature below a beta transus of the titanium alloy for a length of time followed by slow cooling the titanium alloy; and
beta annealing the titanium alloy following completion of the recrystallization annealing steps by heating the titanium alloy to a temperature in a range of 10° to 100° F. above the beta transus of the titanium alloy.
2. The method of claim 1 , wherein the beta transus of the titanium alloy is a temperature between 1800° F. and 1850° F.
3. The method of claim 1 , wherein the temperature to which the titanium alloy is heated during recrystallization annealing is 30° F. to 200° F. below the beta transus of the titanium alloy.
4. The method of claim 1 , wherein the length of time for which the temperature below the beta transus of the titanium alloy is maintained during recrystallization annealing is in a range of 1 hour to 6 hours.
5. The method of claim 1 , wherein following heating the titanium alloy to the temperature below the beta transus of the titanium alloy for the length of time during recrystallization annealing, the titanium alloy is cooled to 1200° F. to 1500° F. at a rate of 50° F. to 500° F. per hour.
6. The method of claim 1 , wherein the beta annealing includes holding the temperature above the beta transus for 30 minutes per inch of thickness of the titanium alloy.
7. The method of claim 1 , wherein the beta annealing further includes holding the temperature in the range of 10° to 100° F. above the beta transus for 15 minutes to 5 hours.
8. The method of claim 1 , further comprising a step of gradually heating then holding the titanium alloy at a temperature 30° F. to 200° F. below the beta transus of the titanium alloy following the slow cooling of the recrystallization annealing step and immediately preceding the step of beta annealing.
9. The method of claim 8 , further comprising the steps of cooling the titanium alloy to a stabilization temperature between 1200° F. to 1450° F. for one or more hours following the beta annealing step and then cooling the titanium alloy to room temperature.
10. A method for heat-treating a titanium alloy, the method comprising the steps of:
recrystallization annealing the titanium alloy, wherein recrystallization annealing includes heating the titanium alloy to a temperature 30° F. to 200° F. below a beta transus of the titanium alloy for a length of time in a range of 1 hour to 6 hours followed by slow cooling the titanium alloy to 1000° F. to 1500° F. at a rate of 50° F. to 500° F. per hour; and
beta annealing the titanium alloy following completion of the recrystallization annealing steps, including heating the titanium alloy to a temperature in a range of 10° to 100° F. above the beta transus of the titanium alloy.
11. The method of claim 10 , wherein the beta annealing includes holding the temperature above the beta transus for 30 minutes per inch of thickness of the titanium alloy.
12. The method of claim 11 , wherein the beta annealing further includes holding the temperature in the range of 10° to 100° F. above the beta transus for 15 minutes to 5 hours.
13. The method of claim 10 , further comprising a step of gradually heating then holding the titanium alloy at a temperature 30° F. to 200° F. below the beta transus of the titanium alloy following the slow cooling of the recrystallization annealing step and immediately preceding the step of beta annealing.
14. The method of claim 13 , further comprising the steps of cooling the titanium alloy to a stabilization temperature between 1200° F. to 1450° F. for one or more hours following the beta annealing step and then cooling the titanium alloy to room temperature.
15. A method for heat-treating a titanium alloy, the method comprising the steps of:
recrystallization annealing the titanium alloy, wherein recrystallization annealing includes heating the titanium alloy to a temperature 30° F. to 200° F. below the beta transus of the titanium alloy for a length of time in a range of 1 hour to 6 hours followed by slow cooling the titanium alloy to 1000° F. to 1500° F. at a rate of 50° F. to 500° F. per hour; and
beta annealing the titanium alloy following completion of the recrystallization annealing steps, including heating the titanium alloy to a temperature above the beta transus of the titanium alloy and holding the temperature above the beta transus for at least 15 minutes per inch of thickness of the titanium alloy.
16. The method of claim 15 , wherein the beta transus of the titanium alloy is a temperature between 1800° F. and 1850° F.
17. The method of claim 15 , wherein the beta annealing further includes holding the temperature above the beta transus for 30 minutes to 5 hours.
18. The method of claim 15 , further comprising a step of gradually heating then holding the titanium alloy at a temperature 30° F. to 200° F. below the beta transus of the titanium alloy following the slow cooling of the recrystallization annealing step and immediately preceding the step of beta annealing.
19. The method of claim 18 , further comprising the steps of cooling the titanium alloy to a stabilization temperature between 1200° F. to 1450° F. for one or more hours following the beta annealing step and then cooling the titanium alloy to room temperature.