Nano-alloying and nano-chemistry of the immiscible elements Fe and Cu in a FeSc-Cu nanoglass

In this study, the alloying of immiscible elements, Fe and Cu, at the atomic level was studied using three-dimensional atom probe tomography (3D APT). The sample was prepared as nanoglass using the inert gas condensation technique with the thermal co-evaporation of Fe₉₀Sc₁₀ alloy and pure Cu. The final composition of the nanoglass was found to be Fe₇₅Sc₁₅Cu₁₀ by energy dispersive X-ray (EDX) spectroscopy. The X-ray diffraction (XRD) pattern indicated the amorphous nature of the sample. The APT analysis of the as-prepared sample showed a homogeneous mixture of Fe and Cu in the presence of Sc throughout the sample. The sample was heat-treated at 100, 200, and 400 °C to examine the miscibility limits with respect to temperature. The sample heat-treated at 100 °C showed a homogeneous distribution of the elements, but at higher temperatures at 200 and 400 °C it showed a de-alloying effect between Fe and Cu. It was observed that Sc tends to alloy with Fe up to 100 °C, but it tends to alloy with Cu at higher temperatures. This preferential alloying of Sc with Fe and Cu is explained by the heat of mixing of FeSc and CuSc alloys. This result will improve our understanding of the nano-alloying of immiscible elements.