Abstract
The work is focused on the preparation of bulk immiscible Cu-Fe-based alloys by powder metallurgy. Three samples with chemical composition Cu70Fe30, Cu70Fe15Co15, and Cu50Fe25Co25 were prepared by mechanical alloying and spark plasma sintering (SPS). Microstructure evolution during sintering and the effect of Co on the resulting microstructure and hardness of the bulk samples were evaluated. Despite the immiscibility of Cu with Fe and Co, the FCC supersaturated solid solution was formed upon mechanical alloying. This supersaturated solid solution was decomposed during SPS and fine microstructure, consisting of separated BCC and FCC phases, was formed. The results showed that cobalt influenced the particle size of milled powders as the particle size of Cu70Fe30 alloy was about an order of magnitude higher compared to other alloys. Cobalt also affected the resulting microstructure of bulk samples, however, its effect on the hardness was negligible. It has been shown that powder metallurgy can be used for the preparation of bulk immiscible alloys with the fine microstructure consists of separate phases, which can be individually alloyed by the selected elements, and therefore, powder metallurgy can be considered as a suitable alternative to the more used casting.
Highlights
In the last years, much attention has been paid to heterogeneous materials due to their ability to overcome strength-ductility trade-off [1,2,3,4]
Creating domains with different properties is an inherent feature of the immiscible alloys, these alloys seem to be a promising group of materials for creating advanced heterogeneous materials with a superior combination of strength and ductility
3.1 Mechanically alloyed powders X-ray diffraction (XRD) analysis showed that despite the positive enthalpy of mixing, at least partially dissolution of Fe and Co into Cu occurred in all samples, resulting in the formation of FCC supersaturated solid solution (SSS)
Summary
Much attention has been paid to heterogeneous materials due to their ability to overcome strength-ductility trade-off [1,2,3,4]. The good combination of strength and ductility is achieved by heterodeformation induced strengthening (HDI) It is the result of the heterogeneous microstructure composed of two domains with different mechanical properties (typically hard and soft domains) that can be caused by microstructural, crystal structure, or/and compositional heterogeneities [5,6]. Immiscible alloys can be noted as heterogeneous materials due to their crystal structure heterogeneity These alloys are characterized by the positive enthalpy of mixing that significantly limited mutual solubility of present elements and the microstructure at room temperature is composed of separated phases of nearly pure elements [7]. Creating domains with different properties is an inherent feature of the immiscible alloys, these alloys seem to be a promising group of materials for creating advanced heterogeneous materials with a superior combination of strength and ductility.
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