中国有色冶金

High temperature titanium alloy ingot was prepared by vacuum induction suspension melting in this paper, and the nominal composition of alloy was Ti-5.8Al-3Sn-8Zr-0.5Mo-0.7Nb-0.25Si. Metallographic microscope, X-ray diffractometer, universal tensile testing machine and thermal simulation testing machine were used to research the evolution of microstructure and mechanical properties of large size titanium alloy ingot from the center to the edge. The experimental results show that the basket structure formed with the wider α-Ti lamella due to the slow cooling rate of the center of the titanium alloy ingot. The lamella width of α-Ti gradually reduced from 6.65μm to 2.99μm as the test location moved from the center to the edge, however, it is worth noting that the width of the α-Ti lamella in the middle position between the center and the edge fluctuated greatly and the distribution was uneven. Tensile properties at room temperature show that the strength from the centerto the edge decreases first and then increases, and the edge position has little difference with the strength of the center because the deterioration effect of defects on mechanical properties weakens the strengthening effect of fine-grained strengthening. The mechanism of high-temperature tensile deformation was mainly controlled by dislocation slip mechanism and diffusion deformation mechanism. At temperatures ranging from 600℃ to 700℃, the higher the temperature, the lower the strength and the better the elongation. The tensile strength of the edge sample was slightly higher than that of the center, and there was a trend of reducing the strength difference as the temperature increases. The hot compression test showed that the limiting compressive strength of the titanium alloy at 950℃ was almost the same for different sampling positions, with the strength of the center position slightly higher than that of the edge position. At 950℃, the deformation mechanism of the material wass completely a high-temperature diffusion-type deformation mechanism.