Microstructure and mechanical properties of in situ (TiC + SiC)/FeCrCoNi high entropy alloy matrix composites

In situ (TiC + SiC) particles (5 vol.% and 10 vol.%, respectively)-reinforced FeCrCoNi high entropy alloy matrix composites were fabricated via vacuum inductive melting method, with equal volume fractions of TiC and SiC particles. X-ray diffraction, scanning electron microscope and energy diffraction spectrum were employed to analyze the microstructure and composition of the samples. The results manifested that the FeCrCoNi matrix is composed of FCC phase, and the in situ particles are homogeneously scattered in the matrix. The presence of reinforcements augmented the ultimate tensile strength from 452 to 783 MPa, and raised the yield strength from 162 to 466 MPa at room temperature, whereas the elongation to fracture was reduced from 70.6% to 28.6%. All the tensile fracture surfaces consisted of numerous tiny dimples, indicating that the composites exhibited ductile fracture. Furthermore, the enhancement of strength ascribes to a combination of thermal mismatch strengthening, load-bearing effect, grain refinement, Orowan strengthening and solid solution strengthening effect, which contribute about 58.0%, 2.4%, 12.3%, 11.1% and 16.2% to the improvement of yield tensile strength, respectively.