فهرست نشریات علمی دسترسی آزاد ایران

In this study, the effect of hot compression and subsequent heat treatment on α globularization and mechanical properties of Ti-8Al-1Mo-1V (Ti-811) alloy with an initial lamellar microstructure was investigated. Heat treatment was performed on hot-deformed samples (at 1000 °C and 0.001 s-1), at temperatures of 800, 850, and 900 °C for durations ranging from 1 h to 5 h. The results showed that the microstructural changes depended on the temperature and time of heat treatment and globular α phase fraction increased with increasing time and temperature. By increasing the heat treatment temperature from 800 °C to 900 °C for 5 h, the volume fraction of globular α phase increased from 68% to 79% and the aspect ratio decreased from 7.2 to 6.2. Microstructural studies showed that the globularization mechanism was controlled by boundary splitting, interface migration, and Ostwald growth. At lower temperatures of 800 °C and 850 °C, the dominant mechanism was boundary splitting by the shearing of α layers, which depended on the amount of pre-strain. At the higher temperature of 900 °C, globularization was controlled by interface migration and Ostwald growth, which were diffusion processes and dependent on heat treatment time. The static globurization kinetics of Ti-811 during heat treatment was well modeled by the modified JMRE equation, with a correlation coefficient (R) of 0.97 and the mean absolute relative error (MARE) of 7.19%. A punching test was applied to evaluate the mechanical properties of the deformed and heat-treated samples. The maximum shear strength and elongation were obtained at 900 °C and a holding time of 2 h, which were equal to 695 MPa and 1.1, respectively.