日本金属学会誌

J. Japan Inst. Metals, Vol. 32, No. 4 (1968),
pp. 334-339

Internal Oxidation of Dilute Ni-Al Solid Solution Alloys

Shoji Goto1 and Shigeyasu Koda1

1The Research Institute for Iron, Steel and Other Metals, Tohoku University, Sendai

Abstract:

The oxidation behavior of solid solution nickel-aluminum alloys was studied at decomposition oxygen pressure of NiO. Five alloys containing 1.37, 2.38, 4.29, 6.37 and 6.55 atomic percent Al were oxidized at 900°, 1000°, 1100°, 1200° and 1300°C for 6, 12, 24, 36, 48, 60 and 72 hours. Studies on the subscale penetration, size and distribution of oxide, and Vickers hardness of the internally oxidized layer have been carried out. The results obtained are as follows.
(1) The relationship between the penetration depth, that is the depth of the internally oxidized layer, and the oxidation time of specimens was well expressed by a parabolic law. (2) Diffusion coefficient of oxygen in the internally oxidized layer was calculated by Wagner's equation. With increase of the dispersed particles, the diffusion coefficient of oxygen increased and this tendency was increased at lower temperature. It was explained by the interfacial diffusion of oxygen between the nickel matrix and dispersed particles. From these results, the diffusion coefficient of oxygen in pure nickel was obtained. (3) The dispersed particles were of platelet on the {110} matrix planes, and had a dendritic structure. (4) The dispersed particles were of crystalline NiAl2O4. (5) An anomalous oxide band was observed at the internal-oxidation front in internally oxidized alloys with high aluminium. (6) The size of the dispersed particles in the internally oxidized layer increased with the distance from the surface of the specimens, and with increasing solute content, the density of dispersed particles became higher. Accordingly, the Vickers hardness of the internally oxidized layer varied, with the distance from the surface.


(Received 1967/9/16)

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