Effect of Cu content on the microstructure and mechanical properties of Fe20Co30Ni10Cr20Mn20 FCC-typed HEAs

This work systematically investigated the influence of Cu content on the microstructure characteristics and mechanical properties of FCC-type Fe20Co30Ni10Cr20Mn20 HEAs. The results showed that the 0 at.% Cu and 2 at.% Cu bearing HEAs exhibited a pure FCC-typed phase. The 5 at.% Cu bearing HEA consisted of FCC-typed matrix and Cu-rich nanoparticles. The 8 at.% Cu bearing HEA presented an FCC-typed matrix, grain boundary (Cu, Ni)-rich phases and intragranular Cu-rich nanoparticles. The small amount of Cu (2 at.%) improved the strength and plasticity by solid solution strengthening. The Cu-rich nanoparticles in 5Cu and 8Cu HEAs further enhanced the FCC-typed matrix via coherency strengthening effects. However, the twin induced deformation was restricted by the Cu-rich nanoparticles due to its higher stacking fault energy. It induced a weaker plasticity of 5Cu HEA. For the 8Cu HEA, the low-hardness grain boundary (Cu, Ni)-rich phase induced the early fracture and resulted in the poorest plasticity.