We are studying heterophase interfaces between molybdenum nitride precipitates and an α-iron matrix on a nanometer scale by electron and atom-probe field-ion microscopies. Fe-2 at.% Mo-0.5 at.% Sn and Fe-2 at.% Mo-0.4 at.% Sb are internally nitrided by annealing in an NH_3 / H_2 atmosphere. Nitridation at 550°C produces coherent thin platelet-shaped molybdenum nitride precipitates, while at 600°C semicoherent coarse plates and spheres also form. Segregation of Sn and Sb is observed at the heterophase interfaces of only the semicoherent precipitates. The loss of coherency, that is the formation of misfit dislocations, is essential for substantial interfacial solute segregation to occur at heterophase interfaces.
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