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The purpose of this study is to investigate the influence of different contents of nano-Al 2 O 3 particles (wt.% = 0–8) on the mechanical properties of FeCoNiCrMn high entropy alloys (HEAs), with the aim of enhancing their strength without compromising ductility. The samples were prepared using mechanical alloying and microwave sintering methods. The microstructure evolution and strengthening mechanisms were evaluated through X-ray diffractometer (XRD), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), and transmission electron microscopy (TEM). The results demonstrate that nano-Al 2 O 3 maintains high stability within composites. An incoherent interface has formed between nano-Al 2 O 3 and HEA matrix, which acts as a barrier to dislocation slip. This interface plays a positive role in enhancing compressive strength and improving plastic deformation capability under compressive loads. In addition, stacking faults are generated in Al 2 O 3 p/FeCoNiCrMn composites, which can induce twinning and improve stress distribution, thereby enhancing the material's capacity for plastic deformation. In terms of mechanical properties, the results indicate that the addition of 2 wt% Al 2 O 3 increased the compressive strength from 998 MPa to 1656 MPa, the yield strength from 125 MPa to 423 MPa, and the compressive strain from 53.7% to 55.2%. Additionally, the inclusion of 4 wt% Al 2 O 3 increased the compressive strength and yield strength to 1440 MPa and 487 MPa, respectively. At a concentration of 2 wt% Al 2 O 3 , the nano-hardness reached its maximum at 5790 MPa, and the elastic modulus was measured to be 230 GPa. Therefore, the incorporation of 2 wt% Al 2 O 3 facilitates the formation of high-quality interfacial structures while enhancing the strength and toughness of the material. The increase in strength can be explained by Orowan strengthening, dislocation strengthening, and thermal mismatch strengthening. Additionally, Hall-Petch strengthening elucidates the significant enhancement in mechanical properties resulting from grain refinement due to the incorporation of second-phase particles.
Wu et al. (Sun,) studied this question.