Method to produce gamma titanium aluminide articles having improved properties

摘要

Gamma titanium aluminide alloys having the composition Ti--(45. 5-47.5) Al--(0-3.0)X--(1-5)Y--(0.05-1.0)W, where X is Cr, Mn or any combination thereof, and Y is Nb, Ta or any combination thereof (at %), are treated to provide specific microstructures. To obtain duplex microstructures, the annealing temperature (T.sub.a) range is the eutectoid temperature (T. sub.e)+100° C. to the alpha transus temperature (T.sub.&agr;)-30. degree. C.; to obtain nearly lamellar microstructures, the annealing temperature range is T.sub.&agr; -20° C. to T.sub.&agr; -1. degree. C.; to obtain fully lamellar microstructures, the annealing temperature range is T.sub.&agr; to T.sub. &agr; +50° C. The times required for producing these microstructures range from 0.25 to 15 hours, depending on the desired microstructure, alloy composition, annealing temperature selected, material section size and grain size desired. The cooling schemes and rates after annealing depend mainly on the microstructure type and stability; for duplex and nearly lamellar microstructures, the initial cooling rate is 5° to 1000° C. /min, while for fully lamellar microstructure, the initial cooling rate is 5° to 100° C./min. The article can be cooled at the initial rate directly to the aging temperature; alternatively, the article can be cooled at the initial rate down to a temperature between room temperature and the annealing temperature, then cooled to room temperature at a cooling rate between the initial rate and water quenching, after which the article is aged. Following annealing, the article is aged at a temperature in the range of 700° C. to 1050. degree. C. for about 4 to 150 hours.