Effect of Alloying and Aging on Morphological Changes from Lamellar to Equiaxed Microstructure of alpha2 + gamma Titanium Aluminides

摘要

The stability of a lamellar structure consisting of alpha2 and y phases in alloys Ti-48A1, Ti-48Al-2Mo, Ti-48Al-4Nb, and Ti-48Al-lMo-4Nb has been studied as a function of aging time and temperature. The alloys were solution treated (1400 deg C, 30 min, and air-cooled (AC)) and aged at 1000 deg C and 1100 deg C for 1, 4, and 16 hours, respectively. The results indicate that the kinetics of lamellae to equiaxed transformation depends on alloy chemistry, aging time, and temperature. The Nb decreases and Mo increases the kinetics of transformation. The combined effect of Nb and Mo results in the highest volume fraction of equiaxed microstructure at a given aging time and temperature. The results have been discussed in relation to microstructural features and have been compared with those reported in other alpha 2 + gamma alloys.