The α phase recrystallization mechanism and mechanical properties of a near-α titanium matrix composite

Abstract

In this paper, the recrystallization mechanism of α phase, microstructure evolution and tensile fracture behavior of in-situ (TiBw + TiCp)/near-α titanium matrix composites have been investigated. The subgrain boundaries formation within αp was caused by strong recovery. The reinforcements played an important role in the recrystallization of α phase. Therefore, the continuous dynamic recrystallization, reinforcements stimulated recrystallization and static recrystallization have a common effect on the αp recrystallization. The room temperature ductility was dominated by the size of silicides, slip transmission between αp and α/β colony, and the morphology of microstructure. The large-scale silicide caused the reduction of ductility at room temperature. After annealed at 1040 °C, the ultimate tensile strength and yield strength at 650 °C of the composites was 745 MPa and 620 MPa, respectively, and the yield strength at 700 °C reached 530 MPa, which has a balance between strength and ductility. The fracture of the composites was associated with the dislocation migration hindered by the boundaries or interaction with each other and the slip of boundaries. Therefore, pores will nucleate in this region due to stress concentration, and the eventual failure were mainly caused by the propagation and connection of pores to big cracks. The above superior performances make the titanium matrix composites have a great application prospect in aerospace fields.