過共晶鉄—りん合金における準安定Fe2Pの安定Fe3Pへの変態

概要

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The author made a study on the isothermal transformation of primary and eutectic metastable Fe2P phase into stable Fe3P phase in hypereutectic Fe-P alloy. Fe-13.6%P alloy melts were solidified in glass so that they contained rod-shaped priamry Fe2P particles embedded in matrices of α-iron and Fe3P in their microstructure. The number of primary Fe2P grains per unit area in the alloy increased as the undercooling of the primary Fe2P increased. Small specimens cut from those alloys were held at 900°C or 930°C for varied holding time and their microstructure were examined. The longer the holding time and the higher the holding temperature, the less fractions of Fe2P and the more fractions of surrounding Fe3P were observed. The holding time for the specimens to reach a definite level of transformation was inversely proportional to the number of Fe2P grains per unit area, which was in good accord with the diffusion-controlled transformation model. Using the diffusion data obtained from the transformation of primary Fe2P particles, an analogous model of the transformation of α-iron and Fe2P eutectic to α-iron and Fe3P eutectic during solidification was constructed. The model explained the relatively easy completion of transformation during solidification.
Japan Foundry Engineering Societyの論文