Optimization of deformation properties in as-cast copper by microstructural engineering. Part I. microstructure

Highlights: • Microstructure of copper was tailored by alloying with different Fe, Co, Sn content. • Microstructure evolution involving grain and iron-rich nanoparticle was investigated. • Mechanism of microstructure evolution was discussed. • Insight to optimize microstructure for excellent mechanical properties was proposed. The microstructural features required to optimize both the strength and ductility of copper are investigated by examining the as-cast pure Cu and Cu-(1.0–3.0)Fe-0.5Co and Cu-1.5Fe-0.1Sn (wt %) alloys. Uniaxial tensile tests show that (Fe, Co)- or (Fe, Sn)-doping improves both the strength and ductility of pure copper. The microstructure evolution with Fe, Co, or Sn doping is characterized by using optical and scanning and transmission electron microscopies. The effects of Fe, Co, and Sn doping on the microstructure clearly show that (i) iron-rich nanoparticles are dispersed inside the grains. The spherical nanoparticles grow in size with increasing Fe content, and when the Fe content exceeds 2.0 wt %, the particles transition into a petal-like morphology. (ii) The microstructure of the alloys (grain size and morphology) is notably influenced by the Fe and Co contents, and the grain size is reduced from an average of 603 μm in pure Cu to an average of 26 μm in the Cu-3.0Fe-0.5Co alloy. (iii) The addition of 1.5 wt % Fe and 0.1 wt % Sn dramatically reduces the grain size to an average of 42 μm, and this reduction is correlated with the appearance of smaller spherical iron-rich nanoparticles. The evolution mechanisms of the iron-rich nanoparticles and grain structure under the alloying effect are discussed.