Ti-55531升温条件下球状和片状α生长及回溶动力学

The microstructure evolution of Ti-55531 alloy with (β+global α) microstructure composition under heating condition of 1 K/min was observed by thermal expansion and SEM, and it was found that the microstructure evolution was α lamellae precipitating, dissolution and α globes dissolution. The kinetics equations of the growth/dissolution of the lamellar precipitate and spherical precipitate were established. The simulation results show that the growth and dissolution of lamellar α is affected by the Gibbs-Thomson effect, which reduces the stability of α lamella tips, thus resulting in the dissolution of α lamella tips below the equilibrium temperature. The elongation of the α lamella tips follows the kinetics controlled by the mixed mechanism of bulk diffusion and interfacial diffusion, while the lateral thickening is controlled by bulk diffusion, and the bulk diffusion controls the dissolution of α lamella. The global α growth at low temperature is controlled by the volume diffusion of stable elements with a lower diffusion rate, and the solubility at high temperature is controlled by the volume diffusion of Al with a higher diffusion rate.