K. Hono

An atom-probe field ion microscope study of the initial stages of oxidation of copper and copper-iron alloy

Abstract The initial oxidation stages of the (111) plane of copper and copper-iron alloys have been studied using the atom-probe field ion microscope (AP-FIM). For pure copper, the concentration depth profiles of the oxide formed ex-situ at 570 K were measured with the atom probe. In the case of the Cu-0.06at%Fe and Cu-1.2at%Fe alloys, the samples were first annealed in-situ in ultra-high vacuum (970 K for 30 s) in order to characterize the surface composition of the alloys prior to exposure to oxygen. Atom probe analysis showed that iron was enriched on the surface for the supersaturated Cu-1.2at%Fe alloy but not for the more dilute Cu-0.06at%Fe alloy. No iron enrichment on the surface, however, was found in either alloy in the equilibrated (aged) condition. Thus, surface enrichment of iron in the supersaturated alloy was concluded to be caused by a heterogeneous form of precipitation rather than by a surface segregation process. In-situ oxidation of the supersaturated Cu-1.2at%Fe alloy at 870 or 970 K led to the formation of both external and internal iron oxide. The thickness of the transition region between the iron oxide and alloy matrix was of atomic dimensions. The iron enrichment on the surface precluded the formation of the usual copper oxides at this early oxidation stage.

Atom-probe study of the initial stage of selective oxidation of Ni from the Cu-Ni alloy system

Abstract The initial oxidation stages of Ni and Ni-Cu alloys have been studied using the atom-probe field ion microscope (AP-FIM). Oxide layers were formed in situ in the FIM chamber on the clean metal surfaces at 1 × 10 −4 Torr (10 −2 Pa) O 2 at 870, 970 or 1070 K for less than l min. The atom-probe analysis on the {111} and {100} surfaces of these oxidized alloys showed that only NiO formed on all of the alloys for this relatively low oxygen partial pressure, although incipient Cu 2 O formation could not be ruled out in a few samples of the Cu-rich alloys. The concentration of oxygen in the NiO fluctuated layer-by-layer in the 〈111〉 direction as expected for its NaCl-type structure. Ne field ion images and atom-probe analyses of the oxidized samples revealed a sharp NiO/metal interface for pure Ni and for the Cu-rich alloys, and a diffuse interface extending over a few atomic layers for the Ni-rich alloys. The NiO and Ni were cube/cube oriented.

Atom-probe analysis of γ-iron precipitates in Cu-1.2at%Fe alloys

Influence de la temperature sur la structure du fer dans les precipites des alliages a base de cuivre. Caracterisation des microstructures par microscopie ionique a emission de champ

Atom-Probe Study of Selective Oxidation of Ni from Cu-Ni Alloy

The initial oxidation stages of Cu-Ni alloys have been studied by atom-probe field ion microscopy (APFIM). Oxide layers were formed in-situ in the FIM chamber on the clean alloy surfaces. The Cu-Ni alloys were oxidized in-situ at 1×10 −4 Torr O 2 at 970 K for less than 1 min. The atom-probe analysis of the {111} and {100} surfaces of the oxidized alloys showed that the oxide was comprised of NiO. The concentration change at the oxide/metal interface was also analyzed by the atom-probe.