  Precipitation-strengthened alloys, such as Ni-base, Co-base and Fe-base
superalloys, show the development of dendrite-like precipitates in the solid
state during aging at near-$\gamma^{\prime}$ solvus temperatures. These
features arise out of a diffusive instability wherein, due to the point effect
of diffusion, morphological perturbations over a growing sphere/cylinder are
unstable. These dendrite-like perturbations exhibit anisotropic growth
resulting from anisotropy in interfacial/elastic energies. Further,
microstructures in these alloys also exhibit "split" morphologies wherein
dendritic precipitates fragment beyond a critical size, giving rise to a
regular octet or quartet pattern of near-equal-sized precipitates separated by
thin matrix channels. The mechanism of formation of such morphologies has
remained a subject of intense investigation, and multiple theories have been
proposed to explain their occurrence. Here, we developed a phase-field model
incorporating anisotropy in elastic and interfacial energies to investigate the
evolution of these split microstructures during growth and coarsening of
dendritic $\gamma^{\prime}$ precipitates. Our principal finding is that the
reduction in elastic energy density drives the development of split morphology,
albeit a concomitant increase in the surface energy density. We also find that
factors such as supersaturation, elastic misfit, degree of elastic anisotropy
and interfacial energy strongly modulate the formation of these
microstructures. We analyze our simulation results in the light of classical
theories of elastic stress effects on coarsening and prove that negative
elastic interaction energy leads to the stability of split precipitates.
