Phase Equilibria on Fe-Cu Based Alloys Used for Electrically Conductive Materials

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It is known that many Fe-Cu based alloys have wide miscibility gap in liquid phase, and by utilizing such phase separation some Fe-Cu based alloys are used as an electrically conductive and a soft-magnetic materials in which fine Cu-rich phase precipitates on iron matrix. Fe-Cu-Si and Fe-Cu-P are typical examples of such alloy systems. Fe-Cu-Si and Fe-Cu-P ternaries are also basic alloy systems formed in the remelting process of incinerated ash which is recently being developed. Moreover, it is important to understand thermodynamic properties of Fe-Cu system to remove copper from remelted steel scrap. In spite of such importance, phase diagrams of Fe-Cu based ternary alloys are not well established. The objective of the present work is to establish phase diagrams and thermodynamic properties of Fe-Cu-Si and Fe-Cu-P ternary alloys. In 1995, solubility of FeSi compound, solid Si in liquid phase and tie lines between two immiscible liquid phases in Fe-Cu-Si system have been measured in the temperature range from 1250ﾟC to 1550ﾟC.As the results, observed phase equilibria differed from the literature phase diagram proposed by Chang et al. In 1996, tie lines between solid iron and copper-rich melt in Fe-Cu-P system were determined at 1250ﾟC by solid-liquid diffusion couple technique. Measured phase equilibria of Fe-Cu-P system also differed from the literature phase diagram. Phase diagrams of Fe-Cu-Si and Fe-Cu-P systems were thermodynamically assessed based on the sub-regular solution model.