Microstructure and creep behavior of directionally solidified TiAl-base alloys

Tensile creep tests were conducted on directionally solidified TiAl alloys to discern the effect of alloying and lamellar orientation. A seeding technique was used to align the TiAl/Ti3Al lamellar structure parallel to the growth direction for alloys of Ti–47Al, Ti–46Al–0.5Si–0.5X (X=Re, W, Mo, and Cr), and Ti–46Al–1.5Mo–0.2C (at.%). Tensile creep tests were performed at 750 °C using applied stresses of 210 and 240 MPa. Aligning the lamellar microstructure greatly enhances the creep resistance which can further be improved by additional alloying.