Ti-55531升温条件下球状和片状α生长及回溶动力学

Thermo-kinetic modeling for the growth/dissolution of α globes and lamella in Ti–55531 under continuous heating condition

摘要:

本文采用升温热膨胀和SEM观察1K/min升温条件下组织组成为(β+球状α)的Ti-55531合金的组织演变，发现组织演变为片状α析出，片状α回溶，球状α回溶。建立了升温条件下片状析出相的生长和回溶动力学方程和球状析出相的生长和回溶动力学方程，模拟这两种形貌α相的动力学行为，并将计算结果与实验测试结果进行比较。模拟结果发现片状α的生长和回溶受Gibbs-Thomson效应影响，Gibbs-Thomson效应降低片状α尖端的稳定性，使得片状α尖端在低于平衡温度发生回溶。片状α尖端的延长遵循体扩散和界面扩散混合机制控制的动力学，而侧面增厚由体扩散控制，片状α的溶解主要受体扩散的影响。而球状α在低温下生长受扩散速率较低的β稳定元素的体扩散控制，高温下回溶受较高扩散速度Al的体扩散控制。

Abstract:

The microstructure evolution of Ti-55531 alloy with (β + global α) microstructure composition under 1K/min heating condition was observed by thermal expansion and SEM, and it was found that the microstructure evolution was α lamellae precipitate, dissolute and α globes dissolute. The kinetics equations of the growth / dissolution of the lamerllar precipitate and spherical precipitate were established. The simulation results showed that the growth and dissolution of lamellar α was affected by the Gibbs-Thomson effect, which reduced the stability of α lamella tips, thus resulting in the dissolution of α lamella tips at lower than 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 control dissolution of α lamella. 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.