Role of interfacial energy anisotropy in dendrite orientation in Al-Zn alloys: A phase field study

Abstract

The influence of interfacial energy anisotropy on dendrite morphology is still not well understood. We investigated the dendrite morphology and solute segregation in Al-Zn alloys using the phase-field method. We observed typical and atypical dendrite orientation transition and three types of dendrite morphology “Christmas tree dendrite”, “seaweed dendrite” and “butterfly dendrite” depending on the anisotropic interfacial energy. Two types of dendrite may undergo the so called-“smooth dendrite orientation transition”, which produces a large amount of solute segregation holes in 〈100〉 dendrites, and liquid grooves in 〈110〉 seaweed and butterfly patterns, thus may significantly impact the mechanical properties of castings. We identified a strong correlation between supersaturation and the formation of liquid holes and liquid grooves as well as the degree of solute segregation. We also proposed that the interfacial energy anisotropy can be related with Zn content by discussing the anisotropic Young’s modulus and experimental pattern of Al-Zn alloys. The inducement of anisotropy and the quantitative relationship between interfacial energy anisotropy, Zn concentration, elastic anisotropy and dendrite orientation deserves attention.