A ductile high entropy alloy strengthened by nano sigma phase

A nanoscale sigma (sigma) phase strengthened Co34.5Cr30Ni26.5Al5.4W3.6 (at, %) high entropy alloy was prepared and showed high strength and ductility. Dual phase microstructure that comprises face-centered cubic (FCC) matrix and nanoscale sigma particles was obtained after thermomechanical procedures. The excellent ductility is attributed to its high strain hardening exponent FCC matrix that strongly favors uniform deformation and prevents crack propagation. The alloy shows an extremely high strain hardening rate and strength due to the interactions between the sigma particles, deformation twins and dislocations. The design concept of deformation twins + nano particles should be considered for the design of additional double-high (strength and ductility) FCC HEAs in future work.