TiB whiskers stimulated the dynamic recrystallization behavior

Abstract

B-containing high temperature titanium alloys were in situ fabricated successfully by casting route. The influences of heat treatment processes on the evolution of microstructures, textures, strengths, elongations and fracture characteristics at room temperature (RT) and high temperature (650 °C) were analyzed. Microstructure investigation revealed that TiB whiskers stimulated the dynamic recrystallization behavior. The volume fractions of primary α phase (VPα) decreased with the increasing solution temperature, while the volume fractions of transformed β phase (VTβ) and widths of secondary α lamellas in transformed β phase (WSα) increased. The inverse pole figures (IPFs) observations illustrated near-equiaxed α grains transformed to ideal equiaxed morphology after 960 °C solution. By the analyzation of pole figues (PFs), after α+β heat treatments, the overall texture intensity increased with the increasing solution temperature, and after β heat treatments, textures with comparatively high intensities were concentrated around various directions. The equiaxed α grains and lamellar α phase had similar main texture components. But the maximum texture intensity of lamellar α phase was obviously higher than that of equiaxed α grains. Moreover, the textures of equiaxed α gains and lamellar α phase exhibited higher similarity after 980 °C solution comparing with after 960 °C solution. Alloy after 980 °C solution exhibited an excellent combination of RT and 650 °C mechanical properties which was ascribed to the microstructure tailoring and the load-sharing effect of TiB whiskers. Fracture of alloys was due to the debonding of TiB whiskers, and the growth and coalescence of micro-voids in matrix and around the cracks of fractured TiB whiskers.