Hot deformation behavior and processing map of novel quasi-network Ti5Si3/TiAl composites

The in-house fabricated quasi-network Ti ₅Si ₃ /TiAl composites showed an excellent combination between light weight and superior high temperature tensile properties in our previous work. However, the deformability was another key factor which determined the Ti ₅Si ₃ /TiAl composites’ potential for high temperature applications in aeronautics and aerospace. Therefore, in this paper the hot deformation behaviors of the novel quasi-network Ti ₅Si ₃ /TiAl composites at temperatures from 900 °C to 1200 °C with strain rates in the range of 0.001–1 s ⁻¹ was systemically investigated. The results showed that the peak flow stress decreased with the increase in the test temperature and the decrease in the strain rate. The thermal compressive deformation constitutive equation was built, and hence the deformation activation energy of the quasi-network Ti ₅Si ₃ /TiAl composite was confirmed to be 564.67 kJ/mol, slightly higher than or similar to the TiAl-based alloys fabricated by traditional casting or powder metallurgy. According to the dynamic material model (DMM), the hot processing maps with the true strain of 0.2–0.5 were established. It can be concluded that the instability area was mainly concentrated in the region of low temperature and high strain rate. Combined with the microstructural analysis, the optimal hot processing parameters were the temperature range of 1125–1200 °C and the strain rate of 0.001–0.01 s ⁻¹ , where a large proportion of dynamic recrystallization occurred. It was noteworthy that the introduction of Ti ₅Si ₃ particles was conducive to accelerating the dynamic recrystallization and limiting the dynamic recrystallization grain growth. Besides, the distribution and size of Ti ₅Si ₃ particles could be regulated by the hot deformation. Finally, the microstructure evolution mechanism in the hot deformation was discussed in detail, this additionally provided the guidance for the practical plastic forming.