Unveiling the mechanisms for Si addition on solidification microstructure and properties of Cu-Fe alloy

Abstract

In this present study, the Si element was intentionally introduced into Cu-20Fe alloy by tuning composition, thus deliberately tailoring resultant microstructure and properties. Accordingly, the effect of Si addition on solidification microstructure and resultant properties of experimental Cu-20Fe-xSi alloys was systematically investigated and elucidated. Microstructural characterization and quantitative analysis demonstrate that the Si addition brings about considerable morphology change (e.g., from original well-developed dendrite to cellular morphology, and eventually being the coral-like morphology) and significant refinement (e.g., from 77.2 ± 15 µm to 7.3 ± 1.3 µm, and then coarsening to 18.9 ± 3.0 µm.), as well as interior sub-microstructure evolution of Fe-rich phase. It is believed that the enhanced undercooling ahead of the solid-liquid interface and the change in the solid-liquid interfacial energy γsℓ resulted from the Si addition should be responsible for such considerable morphology change and significant refinement of Fe-rich phase, respectively. In addition, the morphology and size of Fe-rich phase have a substantial influence on the magnetic and mechanical properties of experimental alloys. It is confirmed that the Fe-rich phase with cellular morphology contributes greatly to the decrease of coercivity by ∼ 60.5% and the enhancement of fracture elongation by ∼ 34.1%, while the dendritic Fe-rich phase with refined size is remarkably beneficial for both improvement of the saturation magnetization (by ∼ 10.6%) and strength (by ∼ 7.2% in ultimate tensile strength). In addition, the corresponding influencing mechanisms have also been clarified through experimental analysis with incorporation of Finite element analysis (FEA) simulation. This present study demonstrates a highly effective and promising method for tailoring solidification microstructure of Cu-Fe alloy by Si addition, which is beneficial for further manipulation of alloy properties either for as-cast or subsequent deformation-processed application.