Preliminary study on the microstructure evolution and deformation behavior of Ti6Al4V-5Cu alloy at low forming temperatures

The cold workability behavior of the Ti6Al4V–5Cu alloy was investigated using a hot compression experiment in the temperature range of 450–650 °C and strain rates interval of 10^− 4 – 10^− 1 s^− 1 with strains of 0.4 and 0.6. Deformation mechanisms and microstructural evolution of the alloy are characterized by means of the Gleeble 3800 compression test, establishing constitutive relationship that relates the microstructure of the deformed specimen with process variables (temperature, strain rate, and strain). Unpleasant product features identified using a scanning electron microscope and an electron backscattered diffraction study, such as edge cracking defects caused by high strain conditions at low deformation temperatures (< 450 °C) and faster strain rates. Grain boundary splitting occurs at the α/α phase interface. The splitting occurred because of the formation of weak structures due to the presence of aluminum as a major phase constituent element, indicating that pseudo super plasticity behavior existed via the sliding of α/α phase grains. The β – phase was found in relatively dense concentrations at the grain boundary teared region of the α/α phase interface, which helped to prevent the cracked edges along the grain boundaries from widening and propagating further. On the single α – phase region, the alloy activation energy (Q) monitored to be 29.58 kJ/mol. The alloy strain rate sensitivity (m) and power dissipation efficiency (η) were also calculated as 0.45 and 22.22%, respectively. Together with the microstructure evolution, true strain-stress curve, and generated processing map, Ti6Al4V–5Cu alloy was found with low metallurgical transformation ability during forming below 650 °C (< 0.39T_m).