Effect Of Anisotropic Surface Tension On Deep-cellular Growth

In the thesis,we investigate the development of the deep-cellular growth,which is one of fundamental subjects in material science,and study the formation of solid-liquid interface microstructure pattern in the field of materials science and processing.By using the matched asymptotic expansion method and the multiple variable expansion method,an asymptotic solution of interface morphology is obtained and the effect of anisotropy on the interface of deep cellular crystal growth in directional solidification is analyzed.The paper contains the following two parts.(1)The effect of anisotropic surface tension and anisotropic interface kinetics on deep-cellular crystal growth in directional solidification is studied.We obtain an asymptotic solution of deep-cellular crystal growth in directional solidification and the corresponding interface morphology.The preferred directions of the anisotropic interface kinetics and anisotropic surface tension are not necessarily the same,and the angle between the preferred directions of the two anisotropies is ?0.It is seen that when the preferred directions of the two anisotropies are the same,i.e.?0=0,as the anisotropic coefficient increases,the total length of the finger increases,the curvature of the interface near the root increases or the curvature radius decreases.It is found that the influence of the anisotropic surface-tension coefficient on interface morphology is more remarkable than the anisotropic interface kinetics coefficient.when the angle 0??0??/4,as the ?0 increases,the total length of the finger decreases,the curvature of the interface near the root decreases or the curvature radius increases;when the angle/r/4??0??/2,as the ?0 increases,the total length of the finger increases,the curvature of the interface near the root increases or the curvature radius decreases.(2)The effect of anisotropic surface tension on the interface morphological stability of deep-cellular crystal during directional solidification is studied.Compared with the directional solidification system of surface tension isotropy,the interface morphological stability of surface tension anisotropy also possesses two types of global instability mechanisms:the global oscillatory instability(GTW-mode).and the low-frequency instability(IF-mode).The results show that as the anisotropic surface tension parameter increases,the unstable domain of global oscillatory instability decreases,the unstable domain of the low-frequency instability increases.