Early Stage of Phase-Separation Processes in FeCr and AlZn Alloys

Phase-separation processes in FeCr and AlZn alloys were studied by a small-angle scattering instrument installed at the KENS pulsed neutron source. Two stages were found in the decomposition process. In the late stage, after annealing time $t$, dynamical scaling holds for the scattering function $S(q, t)$ which exhibits $q^{-4\mathrm{}}$ dependence for high $q$ values. At the earlier stage $S(q, t)$ cannot be described by the same scaling law, and $q^{-2\mathrm{}}$ dependence appears at high $q$. This relation can be well described by the nonlinear theory of Langer, Bar-on, and Miller.