Achieving high strength and ductility of titanium matrix composite reinforced with networked TiB via SPS sintering of core-shell powder and accumulative hot rolling

Abstract

The enhancement of strength and ductility of titanium matrix composites (TMCs) is crucial for lightweighting and expanding their advanced engineering applications. However, it is still a challenge for TMCs to achieve ultrahigh tensile strength with suitable ductility. In this study, a special low-temperature accumulative hot rolling (AHR) process was proposed to regulate the grain/phase boundaries and dislocation structures of TMCs reinforced with networked TiB. Through the AHR process, we have achieved exceptionally tensile strength and yield strength of 1570 MPa and 1460 MPa, respectively, accompanied with a suitable ductility of ∼7.5%. During the AHRed process, the majority of α-Ti grains rotated towards the favorable orientations, which display high SFs for basal slip in ND and prismatic slip in RD, respectively, resulting in the formation of {0002} texture. The accumulation and recovery of dislocations led to the formation of high-density sub-grain boundaries and geometrically necessary dislocations (GNDs) within α-Ti grains. Specifically, the GNDs rose dramatically from 1.06 × 10¹⁴ m⁻² to 8.16 × 10¹⁴ m⁻², whereas the size of α-Ti grains decreased significantly from 6.8 to 1.1 μm. In the β phase grains, secondary phase transformation was induced via the AHR process, resulting in the introduction of high-density nano-scaled secondary α-Ti lamellae (∼4 nm) with a fully coherent interface {110}_BCC//{0002}_HCP. After the AHR process, the crack nucleation and prolongation along the networked TiB was inhibited, resulting in the enhancement of ductility. This special AHR strategy, combining grain/hetero-phase boundary engineering and dislocation engineering, has great potential and universality for designing TMCs with both ultrahigh strength and suitable ductility.