Microstructure and Mechanical Behavior of FeNiCoCr and FeNiCoCrMn High-Entropy Alloys Fabricated by Powder Metallurgy

The present work reports a systematic investigation on phase evolution, microstructure and microstructure–property relationship of two typical face-centered cubic (FCC) structured high-entropy alloys (HEAs), FeNiCoCr and FeNiCoCrMn, prepared via mechanical alloying (MA) followed by spark plasma sintering (SPS). Following 50 h of MA, the two HEAs consisted of a mixture of FCC and body-centered cubic phases. Following SPS, the bulk FeNiCoCr alloy showed a primary FCC phase with a small amount of Cr23C6 and Cr2O3 contaminants, while the bulk FeNiCoCrMn alloy was composed of a primary FCC phase with some (Cr,Mn)23C6 and MnCr2O4 contaminants. The average grain size of the primary FCC phase in the bulk FeNiCoCr alloy was ~ 416 nm, while that of the primary FCC phase in the bulk FeNiCoCrMn alloy was ~ 547 nm. The yield strength, compressive strength and strain-to-failure of the bulk FeNiCoCr alloy are 1525 MPa, 1987 MPa and 24.4%, respectively, whereas those of the bulk FeNiCoCrMn alloy are 1329 MPa, 1761 MPa and 21.9%, respectively. It suggests that the bulk FeNiCoCrMn exhibited lower strength and plasticity in comparison with the bulk FeNiCoCr alloy. Clearly, the smaller grain size of the primary FCC phase in the FeNiCoCr alloy is mainly responsible for the better mechanical performance.