As an important microstructure, columnar crystal growth technology, especially the growth technology of single columnar crystal plays an important role in improving the performances of semiconductor, optical devices and other related products. In many practical applications, because the alloy is composed of multi-component and there is inevitably flow in the melt, it is necessary to study the growth of columnar crystals in multi-component melt with flow separately. The growth of columnar crystal in a ternary undercooled melt subjected to straining flow under non-isothermal conditions is studied, and the approximate analytical expression for growth morphology of columnar crystal is given by using asymptotic method. It can be seen from the expression that straining flow is an important reason for irregular columnar crystal. When analyzing the effect of straining flow on the growth of columnar crystal in ternary melt, it is found that the incoming flow accelerates the growth velocity of the interface, while the outgoing straining flow reduces the growth velocity of the interface, namely, the straining flow makes the interface of columnar crystal deformed. At the same time, it is found that the interface deformation becomes more intense with the increase of flow velocity. The above conclusion can also be applied to the effect of straining flow on the interface morphology of columnar crystal in pure melt and binary melt. The comparison of the effects of straining flow on the interface of columnar crystal among pure melt, binary melt and ternary melt, shows that the interface morphology of columnar crystal in dilute alloy melt is more affected by straining flow than in the pure melt, but the more components are more easily affected by flow. However, the number of components in melt is not a decisive factor for the change of interface morphology of the columnar crystal, but the constitutional undercooling is an important factor for determining the interface morphology of multicomponent alloy. According to the conclusion of this paper, the influence of straining flow on the interface morphology of columnar crystal growth can be quantitatively predicted, which provides the necessary theoretical guidance in accurately controlling the interface morphology in the future.

The effect of anisotropic surface tension on the growth of columnar crystals in ternary melt is studied, and the approximate analytical solution of the growth morphology of columnar crystals is given. It is found that in the initial stage of growth, some parts of the interface grow outward, while some parts first grow inward, and grow outward together with other parts after reaching a certain depth, which makes the columnar crystal interface form a remarkable concave and convex formation. Compared with the case in the pure melt and ternary alloy melt, the component added in the ternary alloy melt decreases the effect of the anisotropic surface tension.

The asymptotic method has been used to investigate the columnar crystals growth subjected to far-field flow in ternary undercooled melt under non-isothermal conditions, and approximate analytical expression of radius and interface growth rate of columnar crystals growth have been given. It is found that the flow causes columnar crystal to grow faster in the upstream direction and slower in the downstream direction, and the growth of columnar crystals in flowing ternary melt is also affected by impurity content, that is, the higher the impurity content, the faster the columnar crystal grows in the upstream direction and the slower the growth in the downstream direction. The growth problem of columnar crystals from multi-component melt under flow is more complicated than that of a pure melt because it involves both the heat transport process and mass transport in the solute. The results show that the deflection angle of columnar crystals is a result of interaction of flow and impurity content.