DEFORMATION AND RECRYSTALLIZATION BEHAVIOR OF THE TIAL PHASE CONSTITUTING THE TIAL/TI3AL LAMELLAR STRUCTURE OF TI-RICH TIAL COMPOUNDS

We have grown TiAl crystals of a nearly stoichiometric composition composed of a single lamellar grain as well as those composed of two lamellar grains and studied their deformation behaviour at room temperature. The deformation behaviour of lamellar grains depends strongly on their lamellar orientation. Yield stress is high for uniaxial loading perpendicular or parallel to the lamellar boundaries (the hard mode of deformation), while it is low for uniaxial loading at an intermediate angle (the easy mode of deformation). The tensile elongation for the easy mode of deformation can be as large as 20% at room temperature. By utilizing such easy mode of deformation, TiAl can be rolled up to 50% reduction in thickness at room temperature. Microstructures resulted from annealing of cold-rolled TiAl have been found to depend on the amount of reduction in thickness. This paper summarizes the results of a systematic study on the deformation and recrystallization of TiAl crystals with the lamellar structure.