TY - JOUR
T1 - Subnanometer-scale chemistry and structure of α-iron/molybdenum nitride heterophase interfaces
AU - Isheim, Dieter
AU - Seidman, David N.
N1 - Funding Information:
This research was supported by the National Science Foundation (Bruce A. MacDonald, grant officer) under Grant No. DMR-9728986. The high-resolution electron microscopy was performed at the Materials Science Division, Argonne National Laboratory, and Dr. Rosann Csencsits is thanked for cheerful assistance. DI received partial support through the Max Planck Research Prize of D.N.S. and from the Deutsche Forschungsgemeinschaft. The authors thank Ms. P. Epps, Mr. M. Potter, Mr. A. Pyzyna, Ms. E. Siem, Mr. E. Spoerke, and Ms. I Uttayarat for their contributions to this research as a result of a series of undergraduate research projects, which were supported by the REU program of the National Science Foundation.
PY - 2002/8
Y1 - 2002/8
N2 - The local chemistry and structure of α-iron/molybdenum nitride heterophase interfaces is studied on a subnanometer scale by atom-probe field-ion microscopy (APFIM), three-dimensional atom-probe microscopy (3DAPM) and both conventional transmission electron microscopy (CTEM) and high-resolution electron microscopy (HREM). Molybdenum nitride precipitates are generated by annealing Fe-2 at. pct Mo-X, where X = 0.4 at. pct Sb or 0.5 at. pct Sn, at 550 °C or 600 °C, in an ammonia/hydrogen mixture. Internal nitridation at 550 °C produces thin, coherent platelet-shaped molybdenum nitride precipitates. Nitridation at 600 °C generates a much coarser structure with semicoherent thick plate-shaped and spheroidal precipitates in addition to the thin-platelet structure. The APFIM and 3DAPM analyses of the heterophase interfaces show substantial segregation of the solute species Sn and Sb only at the coarse precipitates, with Gibbsian interfacial excesses of up to 7 ± 3 nm-2, whereas the broad faces of the thin platelets have no detectable segregation. The TEM and HREM analyses show that the coarse precipitates are semicoherent, whereas the thin platelets are either coherent or have much fewer misfit dislocations than geometrically necessary. This demonstrates that Sn and Sb segregation is related to the presence of misfit dislocations at the interfaces of the coarse precipitates.
AB - The local chemistry and structure of α-iron/molybdenum nitride heterophase interfaces is studied on a subnanometer scale by atom-probe field-ion microscopy (APFIM), three-dimensional atom-probe microscopy (3DAPM) and both conventional transmission electron microscopy (CTEM) and high-resolution electron microscopy (HREM). Molybdenum nitride precipitates are generated by annealing Fe-2 at. pct Mo-X, where X = 0.4 at. pct Sb or 0.5 at. pct Sn, at 550 °C or 600 °C, in an ammonia/hydrogen mixture. Internal nitridation at 550 °C produces thin, coherent platelet-shaped molybdenum nitride precipitates. Nitridation at 600 °C generates a much coarser structure with semicoherent thick plate-shaped and spheroidal precipitates in addition to the thin-platelet structure. The APFIM and 3DAPM analyses of the heterophase interfaces show substantial segregation of the solute species Sn and Sb only at the coarse precipitates, with Gibbsian interfacial excesses of up to 7 ± 3 nm-2, whereas the broad faces of the thin platelets have no detectable segregation. The TEM and HREM analyses show that the coarse precipitates are semicoherent, whereas the thin platelets are either coherent or have much fewer misfit dislocations than geometrically necessary. This demonstrates that Sn and Sb segregation is related to the presence of misfit dislocations at the interfaces of the coarse precipitates.
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U2 - 10.1007/s11661-002-0355-3
DO - 10.1007/s11661-002-0355-3
M3 - Article
AN - SCOPUS:0036694642
VL - 33
SP - 2317
EP - 2326
JO - Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science
JF - Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science
SN - 1073-5623
IS - 8
ER -