Atomic level microstructural characterization by APFIM

Atom probe field ion microscopy has been used to characterize Ni aluminides in addition to changes in microstructure of pressure vessel steels as a result of exposure to neutron irradiation. Ultrafine intragranular Cu precipitates and P segregation to grain and lath boundaries have been quantified in the pressure vessel steels. In boron-doped Ni{sub 3}Al, the B additions were found to segregate to dislocations, low angle boundaries, antiphase boundaries, stacking faults, and grain boundaries. In boron-doped NiAl, B segregation to grain boundaries and ultrafine MB{sub 2} precipitates were observed. In Mo-doped NiAl, enrichments of Mo, C, N/Si, B, and Fe were observed at the grain boundaries together with Mo precipitates and low Mo matrix solubility