Characterization of immiscible Fe-Cu alloys through a quantitative composition-microstructure-property relationship

초록

Phase topology plays a decisive role in determining the balance between mechanical strength and thermal conductivity in immiscible Fe-Cu alloys; however, its quantitative contribution has remained largely unexplored. In this study, cast Fe-Cu alloys containing 10-80 wt% Cu were systematically investigated to establish a quantitative composition-morphology-property relationship. Quantitative image analysis revealed that the characteristic phase size increased from 12.1 to 39.6 mu m, the connectivity index increased from 0.09 to 0.79, and the interface density increased from 4.17 to 10.21 mm-1 as the microstructure evolved toward a bicontinuous morphology, followed by a subsequent decrease with further increasing Cu content. This systematic morphology transition from a continuous Fe-rich network to a bicontinuous structure and finally to a continuous Cu-rich network governed the evolution of mechanical and thermal properties. The continuous Fe-rich network exhibited the highest ultimate tensile strength (356.6 MPa), whereas the continuous Cu-rich network achieved the highest thermal conductivity (168.7 W center dot m(-1)center dot K-1). In contrast, the bicontinuous morphology provided the optimum balance between tensile strength (328.8 MPa) and thermal conductivity (123.4 W center dot m(-1)center dot K-1) owing to the simultaneous continuity of both phases. More importantly, the proposed quantitative morphology descriptors successfully correlated phase topology with load-transfer and heat-conduction pathways, establishing quantitative composition-morphology-property relationships. These relationships demonstrate that phase topology, rather than phase fraction alone, governs the strength-thermal conductivity relationship and provide a practical morphology engineering strategy for designing immiscible Fe-Cu alloys with tailored multifunctional performance.

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