Hot Deformation Behaviors in Ti-6Al-4V/(TiB + TiC) Composites

Abstract

Thermal compression testing was investigated using the Gleeble 3800 thermal simulator, and thermal deformation behavior of particle-reinforced titanium matrix composites (TMCs) was studied under deformation temperatures of 750–900 °C, strain rates of 0.001–1 s−1, and experimental deformation of 60%. According to obtained flow stress curves, the hot deformation characteristics were analyzed. Based on the Arrhenius hyperbolic sinusoidal model, the constitutive equation at high temperature was established. Based on the theory of dynamic material models, a hot processing map of TMCs at high temperature was established, and the peak region of power dissipation rate and the instability region in the hot processing map were both determined. At the same time, the corresponding microstructures in the peak power dissipation rate and rheological instability regions were observed. The results showed that flow stress decreased with increasing deformation temperature and increased with increasing strain rate. The thermal deformation activation energy of titanium matrix composites was 301.8 kJ/mol. The Ti-6Al-4V/(TiB + TiC) composites possessed only one instability zone under high-temperature compression at a strain of 0.5, with corresponding temperatures at 750–840 °C and strain rates at 0.1–1 s−1. The optimal thermal deformation parameters included corresponding temperatures of 830–880 °C and strain rates of 0.001–0.05 s−1. The microstructures corresponding to optimal hot working parameters in processing maps were more homogeneous than the microstructures in the instability zone, including the distribution uniformity of reinforcement and the degree of dynamic recrystallization, and no instability phenomena including abnormal grain growth, microcracks or intensive fracture of reinforcements were found, indicating that the hot processing map had a positive guiding effect on the option of desirable material thermal-working parameters.