Small-Angle Neutron Scattering Study of Phase Decomposition in Fe–Cu Binary Alloy

Small-angle neutron scattering (SANS) measurements were carried out in order to investigate the structure change during early stage of phase decomposition in an Fe-1.17 at% Cu alloy. The integrated intensity first increased and then saturated beyond 2·104 s aging at 773 K, while the Guinier radius increased with the time exponent of 1/3, emphasizing the coarsening process of precipitates. The peak hardness was observed, when the Guinier radius reached 2.8 nm. The intensity ratio of magnetic scattering component to nuclear one has been analyzed in terms of chemical composition and internal structure of precipitates. Its change during aging was concluded to relate that bcc copper-rich clusters decomposed from the supersaturated α Fe phase transform mainly to the ε Cu phase.