Phase Field Method Simulation Of Ti-Al Alloy Dendrite Growth

In the process of metal solidification,the microstructure has an important influence on the excellent physical properties of the casting,so the study of the solidification structure is of great help to improving the performance of the casting.The rise of the microstructure simulation method has a propelling effect on the study of the solidification process of metals,and has provided help for in-depth study of the microstructure structure,which is more efficient and accurate.As a powerful simulation method,the phase field method can be combined with a variety of external fields and multiple disciplines.It has a wide range of applications and deep development potential.In this paper,the Karma thin interface phase field model is used to simulate the following aspects of Ti-Al alloy.1.The effects of different undercooling,supersaturation,and noise on the growth of equiaxed dendrites are simulated.The simulation results show that the undercooling will affect the degree of development of primary and secondary dendrites,and cause micro-segregation of solutes;supersaturation will also change the micro-segregation of solutes,affecting the tip radius and steady-state coefficient of the dendrites;noise will cause the asymmetric growth of secondary dendrites,but it has little effect on the morphology of primary dendrite and the steady-state growth of dendrite tip.2.The dendrite growth process of directional solidification was simulated,and the influence of the pulling speed and noise on the growth morphology of the directional solidification columnar dendrites was studied.The simulation found that the pulling speed would cause the solute enrichment in the secondary dendrite interstitials,competitive growth and fusion of dendrites appear.The ratio of secondary dendrites will show the degree of development of dendrite morphology;noise will affect the symmetrical growth of secondary dendrites on both sides of the main dendrite,and the dendrite morphology on both sides will change.The difference is large,and it has a slight influence on the morphology of the dendrite tip.3.The growth process of tilted dendrites was simulated,the morphology of tilted dendrites with different tilt angles were analyzed,and the 45° tilt angle of the special morphology was introduced in detail,and the temperature gradient on the growth of tilted dendrites was simulated.The simulation results show that the asymmetry behavior of the secondary dendrite arms increases when the tilt angle increases.When the tilt angle is 45°,the secondary dendrites merge,and the growth of the main dendrites is inhibited and replaced by new dendrites.The greater the temperature gradient is,the number of secondary and tertiary dendrites will increase and become coarser,and the tip of the tertiary dendrite will produce small protrusions that grow along the direction of the temperature gradient.The tip of the tilted dendrite is lower than the normal dendrite in the tilt direction(x axis),that is,the growth of the tip of the tilted dendrite will be hindered by the normal dendrite.When the normal dendrites and the inclined dendrites grow together,the inclined dendrites are eliminated by the normal dendrites,which is consistent with the phase field simulation results.