Hall-Petch relation in two-phase TiAl alloys

Abstract

The Hall-Fetch relation in lamellar-gamma duplex structures of TiAl alloys has been evaluated using Fan and Miodownik's model, by assuming that the friction stress varies linearly with the lamellar volume fraction. The results reasonably predict the strength of lamellar-gamma duplex structures at various grain sizes and volume fractions. The individual contributions from three constituting boundaries, lamellar-lamellar (alpha-alpha), gamma-gamma (gamma-gamma), and lamellar-gamma (alpha-gamma) boundaries to the overall strengthening have been calculated as a function of alpha volume fraction: the alpha-gamma phase boundaries are not effective obstacles to dislocation motion. The alpha-alpha grain boundaries are rather the strongest obstacles to dislocation motion.