Effect of Homogenization Heat Treatment on Channel Segregation in Nb47Ti Alloy Ingot

Abstract:

Channel segregation in Nb47Ti alloy is prone to occur during vacuum arc remelting (VAR), which significantly degrades its processability. Molecular dynamics simulations reveal that for the Ti-Nb system under isothermal holding at 1170 ℃, the mean squared displacement (MSD) of Ti and Nb increases with the increase in Nb content, indicating that homogenization treatment effectively alleviates microsegregation. In Nb47Ti alloy, solute atoms Nb exhibit significantly stronger displacement amplitudes and diffusion trajectories than the Ti matrix. The effects of homogenization heat treatment at 1170 ℃ for 5.5 and 10 h on the microsegregation and channel segregation of Nb47Ti ingot with diameter of 520 mm were analyzed. The results show that the segregation index of microsegregation decreases by 0.27% and 0.53% after homogenization, but no significant improvement is observed in the morphology, quantity, or size of channel segregation. Increasing the heat treatment temperature or prolonging the duration has an extremely minimal effect on reducing channel segregation, and may lead to excessive hydrogen content issues.