日本金属学会誌

J. Japan Inst. Metals, Vol. 40, No. 11 (1976),
pp. 1164-1172

Morphology and Growth Kinetics of Delta-eutectoid Structure Produced by Carburization

Takashi Saito1, Taketo Sakuma2 and Taiji Nishizawa2

1Graduate School, Tohoku University, Sendai
2Department of Materials Science, Faculty of Engineering, Tohoku University, Sendai

Abstract:

Delta-eutectoid structure consisting of austenite (transformed to martensite on quenching) and alloy carbide was obtained by carburization of α Fe-M binary alloys. The carburization temperature for obtaining the eutectoid structure ranged from 850 to 1300°C depending upon the content of the alloying element M. The eutectoid structure obtained was lamellar in α Fe-Cr alloys and mostly fibrous in α Fe-V and α Fe-Ti alloys. In α Fe-Mo and α Fe-W alloys, the structure was intermediate between lamellar and fibrous. The growth rate v was estimated to be controlled by the diffusion rate of carbon atoms through the austenite in the eutectoid structure. The inter-lamellar spacing S was related to the depth of the reaction front ξ as given by the equation: S2∼eqk⋅ξ , where k is a constant depending upon the diffusivities of carbon and the alloying element M, the carbon content in the austenite, and the composition of the carbide. The relationship between growth rate and inter-lamellar spacing was found to be vS2∼eq4DMI⋅λ , where DMI is the diffusion coefficient of the alloying element M along the interface at the reaction front, and λ is the thickness of the interface.


(Received 1976/04/28)

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