  The compositional diffusional-trajectories for a phase separation of
gamma(f.c.c.)/gamma-prime(L12) phases are studied in a quaternary
Ni-10Al-8.5Cr-2Re alloy, aged at 700 deg.C for 0 to 1024 h, utilizing
atom-probe tomography (APT). As the gamma-prime(L12)-precipitates grow, the
enrichments of Ni, Cr, and Re and depletion of Al on the gamma(f.c.c.)
matrix-side develop as a result of diffusional fluxes crossing the
gamma(f.c.c.)/gamma-prime(L12) interface.The experimental (APT) compositional
trajectories of the two-phases, gamma(f.c.c.)/gamma-prime(L12), are displayed
in a quaternary phase-diagram, employing a tetrahedron, and compared with the
Philippe-Voorhees (P-V) coarsening model which includes the off-diagonal terms
in the diffusion tensor for the multi-component system.
