  Although the anisotropy of the solid-liquid interfacial free energy for most
alloy systems is very small, it plays a crucial role in the growth rate,
morphology and crystallographic growth direction of dendrites. Previous work
posited a dendrite orientation transition via compositional additions. In this
work we examine experimentally the change in dendrite growth behaviour in the
Al-Sm (Samarium) system as a function of solute concentration and study its
interfacial properties using molecular dynamics simulations. We observe a
dendrite growth direction which changes from <100> to <110> as Sm content
increases. The observed change in dendrite orientation is consistent with the
simulation results for the variation of the interfacial free energy anisotropy
and thus provides definitive confirmation of conjecture in previous works. In
addition, our results provide physical insight into the atomic structural
origin of the concentration dependent anisotropy, and deepens our fundamental
understanding of solid-liquid interfaces in binary alloys.
