| Abstract Scope |
Phase-separation of a Ni-10Al-8.5Cr-2Re at.% alloy aged at 973 K is studied from 0 to 1024 h, by atom-probe tomography, where the gamma (f.c.c.) and gamma-prime (L12) composition trajectories are displayed in a tetrahedron, whose apexes correspond to Ni, Al, Cr and Re. The gamma-prime precipitates are nucleated deep inside the gamma-prime phase-field and they have a composition trajectory that evolves toward a curved gamma-prime solvus-surface. The composition trajectory of the gamma (f.c.c.)-phase commences in the (gamma plus gamma-prime phase field) at the mean composition of this quaternary alloy, which moves along a trajectory toward the curved conjugate gamma-solvus surface. The composition trajectory of the gamma-prime precipitates encompasses nucleation, growth and coarsening and it is curvilinear. The composition trajectory of the gamma phase reflects changes in the matrix’s composition. The tie-line between gamma- and gamma-prime-phases is determined by the end-point compositions of the two-phases on the two conjugate solvus surfaces. |