Strain rate-dependent high-temperature tensile properties of additively manufactured Ti6Al4V: microstructural study and residual stress analysis
摘要
Ti6Al4V is used in lightweight high-temperature applications due to its unique properties, such as higher specific strength, excellent energy absorption capacity, and superior high-temperature plasticity. In the present study, an attempt has been made to investigate the combined effect of strain rate and high-temperature on the tensile behavior, microstructural characteristics, and fracture mechanism of Wire Arc Additively Manufactured (WAAMed) Ti6Al4V. Furthermore, strain rate sensitivity of Ti6Al4V at room and elevated temperature (700 °C) has also been evaluated. The comparative analysis of strength coefficient and strain hardening index ascertained the dominance of work hardening in Ti6Al4V tested at room temperature. However, thermal softening of Ti6Al4V at 700 °C, governed by dynamic recrystallization, is found to result in 352.31% and 370.69% improvement in the fracture strain tested at 0.01 s−1 and 0.001 s−1 strain rates, respectively. Furthermore, a comparative analysis of high-temperature tensile test results showed that WAAM-built Ti6Al4V performed better than sheet metal-formed Ti6Al4V counterpart, while the experimental flow stress and deformability are found to be comparable to other conventionally fabricated Ti6Al4V. Microstructural study of high-temperature processed Ti6Al4V confirmed the evolution of coarse globularized α phases through boundary-splitting mechanism, resulting in an increase of slip length. This research attempt also reveals that temperature-sensitive grain dislocation density, misorientation, and deformation twins influence texture intensity and deformation characteristics. Moreover, high-temperature processing is found to induce compressive residual stress, contributing to its improved flow behavior and high-temperature deformability.
Graphical abstract