Insight into the evolution of voids in TiBw-reinforced titanium matrix composites during isothermal compression

Abstract

The evolution of two distinct void types formed during isothermal compression of Ti55-TiBw composites in the α+β region was systematically investigated through quantitative analysis from various deformation parameters and deformation regions. The results showed TiB whiskers (TiBw) impeded dislocation motion, leading to local stress concentration in the matrix. The stress concentration might result in either TiBw fracture or matrix-reinforcement interfacial debonding, consequently generating voids in the titanium matrix. The two types of voids exhibited distinct sensitivities to variations in deformation parameters. The average numbers of voids per unit area resulting from the fracture of TiBw exhibited more sensitivity to the variations in deformation temperature. In contrast, the voids generated by interfacial debonding demonstrated greater sensitivity to the changes in strain rate. Importantly, the factors influencing void closure were not limited to merely the increasing of strains. The strain state also played a crucial role, as compressive strain facilitated void closure by the sufficient flow of titanium matrix, whereas tensile strain significantly hindered the void closure. Moreover, (Nd, Sn)-rich second-phase particles embedded in reinforcements might have a deleterious effect on the integrity of TiBw, inducing crack initiation and propagation in TiBw.

Keywords

• Titanium matrix composites (TMCs)
• TiB whisker (TiBw)
• Isothermal compression
• Evolution of voids
• Finite-element stimulation