Microstructure characterization and mechanical behaviors of a hot forged high Nb containing PM-TiAl alloy

摘要

In this work, the effects of deformation on the microstructure and mechanical behaviors of TiAl alloy were investigated. Deformed microstructure observation was characterized by scanning electron microscopy, electron back scattered diffraction technique, transmission electron microscopy and DEFORM-3D software. Results indicated that the core area of the TiAl pancake was characterized by completely dynamically recrystallized microstructures, however some residual lamellar colonies can be observed near the edge area, which are primarily caused by a temperature drop and inhomogenous plastic flow. The main softening mechanism is dynamic recrystallization of γ grains. The as-forged alloy exhibited excellent mechanical properties at both room temperature and high temperature. Tensile test results showed that the ultimate tensile strength of the alloy increased from 832 MPa at room temperature to 853 MPa at 700 °C, while the elongation increased from 2.7% to 17.8%. Even at the temperature of 850 °C, the ultimate tensile strength maintained 404 MPa, and the elongation increased to 75%. The as-forged alloy also exhibited remarkable low-temperature superplasticity at 850 °C, with an elongation of 120%.