Effect of Cu on the strengthening and embrittling of an FeCoNiCr-xCu HEA

The effect of Cu concentration on the microstructure and mechanical properties of FeCoNiCr-xCu HEAs was investigated. The results showed that low Cu concentrations (less than ∼5 at. %) contributed to a solid solution strengthening effect. The solid solution Cu atom strengthened the yield strength and ultimate tensile strength together. When the Cu concentration reached approximately 7 at. %, larger numbers of nano Cu-rich particle precipitated from the FCC matrix. The nano Cu-rich particle had a strengthening effect and further increased the yield strength and ultimate tensile strength. When the Cu concentration reached approximately 13 at. %, the weak continuous Cu-rich phase formed between dendrites. The early fracture of the Cu-rich phase dramatically decreased the ultimate tensile strength and elongation.