SANS Study of Phase Decomposition in Fe-Cu Alloy with Ni and Mn Addition.

Small-angle neutron scattering (SANS) measurementswere carried out to investigate the structural change during the early stage of phase decomposition in Fe-Cu-Ni-Mnquaternary alloy. Data analysis of scattering intensities showed that the nuclear Guinier radius becomes larger than the magnetic one beyond about 2nm. This is suggested to be attributable to the formation of segregated layer enriched by Ni and Mn around fcc copper-rich precipitate. This segregation was confirmed directly by atom-probe (AP) analysis and approved from a thermodynamic point of view. The calculated SANS intensities are well fitted to experimental data of both magnetic and nuclear cohponents of neutron scatterings. Addition of Ni and Mn in Fe-Cu binary alloy was suggested to promote the precipitation reaction of 8-Cu phase.