Microstructure evolution, deformation behavior and manufacture design of TiAl matrix composites reinforced with in-situ borides precipitation

Abstract

Phase transformation and borides precipitation caused by boron addition influence microstructure evolution and deformation behavior of in-situ TiAl matrix composites. Dynamic recrystallization mechanism and dynamic recovery mechanism were investigated by isothermal compression tests, scanning electron microscopy and transmission electron microscopy, etc. The value of apparent deformation activation energy (Q) of present composites is calculated to be 691.506 kJ/mol. In the temperature range of 1100−1200 °C, nucleation and growth of recrystallized γ and α grains promoted by TiB obstacles dominate the deformation below or above Tα2→α. The dynamic recovery of α phase dominates the deformation in condition with low strain rates at 1250 °C. Boron addition increases the fraction of α phase and decreases the transformation temperatures of γ→α and α2→α, which promotes the nucleation and growth of recovered α grains during the loading. Deformation mechanisms and processing performance were also clarified based on the reestablished constitutive model.