Study on hot deformation behavior and processing map of a Ti-47.5Al-2.5V-1.0Cr-0.2Zr alloy with a fully lamellar microstructure

Abstract

The hot deformation behavior of a Ti-47.5Al-2.5V-1.0Cr-0.2Zr alloy was investigated through thermal simulation experiments. The thermal deformation temperature range was 1050–1200 °C with a strain rate of 0.001–1 s−1. The connections between the stress, strain rate, and temperature were established using a constitutive equation, which included the influence of strain. The correlation coefficient between the calculated stress and the experimental data was 0.991, which indicated that the predicted stress curve was consistent with the experimental results and that the constitutive relationship could accurately predict the deformation behavior. The processing map indicated the optimum hot deformation ranges of temperatures and strain rates were determined to be 1140–1180 °C and 0.001–0.006 s−1, respectively. The proportion of dynamic recrystallization(DRX) and low dislocation density regions was higher in the optimum hot deformation region than in the instability region, and no instability phenomena, such as cracking, were found; hence, the thermal processing map predictions agreed well with the microstructure. The dominated deformation mechanism of the TiAl alloy mainly depended on DRX, and the movement of dislocations and twins were the typical deformation mechanisms.