Compressive response and microstructural evolution of bimodal sized particulates reinforced (TiB+La2O3)/Ti composites

Highlights: • The hot deformation behavior of (TiB+La₂O₃)/Ti composites is investigated. • Bimodal-sized reinforcements strongly affect deformation behavior of the composite. • The optimal hot working window for the composites is 900–950 °C/0.01–0.1 s⁻¹. • The CDRX of primary α and globularization of lamellar α are found in α+β region. The hot deformation behavior and microstructural evolution of bimodal sized particulates reinforced (TiB+La₂O₃)/Ti composites are investigated in the temperature range of 850–1100 °C and strain rate range of 0.001–1 s⁻¹ using isothermal compression tests. The constitutive equations in different phase regions are established in terms of the flow stress data, and the apparent activation energies are calculated to be 753 kJ/mol in α+β phase region and 185 kJ/mol in β phase region, which are much higher than those of matrix alloy due to the incorporation of bimodal sized reinforcements. The optimal hot processing window for (TiB+La₂O₃)/Ti composites is determined at 900–950 °C/0.01–0.1 s⁻¹, which is associated with the continuous dynamic recrystallization (CDRX) of primary α grains and dynamic globularization of lamellar α. The necklace recrystallization of β grains and dynamic recovery (DRV) of lamellar α are observed in β phase region, and the instability mechanisms include inhomogeneous deformation and breaking or debonding of TiB whiskers. Additionally, TEM observations are used to study the effects of reinforcements on microstructural evolution. The results indicate that both micro-sized TiB and submicro-sized La₂O₃ can impede dislocation movement and TiB can facilitate the dynamic recrystallization (DRX) of α phase and grain refinement.