Strengthening mechanism in a high-strength carbon-containing powder metallurgical high entropy alloy

A carbon-containing FeCoCrNiAl_0.5 high entropy alloys (HEAs) with high tensile strength was fabricated by powder metallurgy (P/M) method. The P/M process includes gas atomization and hot extrusion of pre-alloyed HEA powder. The microstructural evolution and mechanical properties were systematically investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and tensile tests. The results showed that the gas-atomized HEA powder was of dual phase, including face centered cubic (fcc) phase and B2 phase. Hot extrusion caused the precipitation of M₂₃C₆ carbides, the formation of dislocations and the refinement of microstructure. The as-extruded HEA exhibited a tensile strength as high as 1093 MPa and an elongation of ∼12.4%. The contributions of different strengthening mechanisms were quantitatively calculated, and it was found that the grain boundary strengthening and the dislocation strengthening are the main strengthening mechanism.