Formation of varying dendritic morphologies in a directionally solidifying Ga-In-Bi alloy

Abstract

Solidification of a ternary Ga-In-Bi alloy under a thermal gradient ≈ 1.8 K/mm with a moderate cooling rate 0.01 K/s was performed with in-situ observation using X-ray radiography. Similar to the solidification of a binary Ga-In alloy, buoyancy convection developed in the system due to a large density difference between the alloy components. Yet, it was found that contrary to the binary system, the primary arms of the ternary solid structure not only adapt their velocity to the variation of the local concentration ahead of their tips but may also change continuously or abruptly their growth direction. A closer look on the system revealed that the deviation of the growth direction happened via branching. Alternatively, some of primary arms demonstrated multiple splitting and intense yet retarded growth of the secondary arms.