Estimation of rod-like phase spacing in melt-grown eutectic composites

Directional solidification of rod-like eutectic is an important route to produce in situ composites. The rod-like phase spacing of composites is a crucial parameter in determining the properties of the materials. In this study, the rod-like phase spacing of melt-grown in situ eutectic composites is estimated by the method that is established based on the classical Jackson-Hunt theory and completed by considering the minimum undercooling principle in eutectic solidification at steady state. The density difference between the solid phases is also considered when calculating the diffusion field in the liquid. It is found that the rod-like phase spacing of in situ eutectic composites is generally a not unique value but displays a finite range under fixed growth conditions. Also, the range width, which decreases with increasing growth rate and vice versa, is only dependent on the intrinsic properties of an alloy at a given growth rate. By comparing with the experimental observations, the results show that the predicted spacings are in reasonable agreement with experimental data for nonfaceted-nonfaceted Succinonitrile-(D)camphor, MnSb-Sb, and Al-Al₃Ni alloys and faceted-nonfaceted MnBi-Bi system when growing in a coupled manner.