Effect of carbon on microstructure and mechanical properties of FeMnNiCrAl high entropy alloy

The effect of C on microstructure and mechanical behavior upon compression test of Fe32Mn32Ni8Cr8Al20 high entropy alloys (HEAs) has been investigated by electron microscopies, atom probe tomography (APT) and mechanical testing. The results show that addition of C leads to the formation (C, Mn, Cr)-rich FCC phase and its volume fraction increases with increasing C content. Meanwhile, C addition produces nanoscale L21 particles. The formation of soft FCC phase improves compressive strain of HEAs and decrease its yield strength. However, the formation of nanoscale L21 particles enhances evidently yield strength via precipitation strengthening. Balance strength and ductility was achieved when alloying with 2.0 at.%. Further increasing C addition would result in decreased population of L21 particles and excessive soft FCC phase, leading to undesirable softening. It is thus concluded that C alloying is promising in manipulating microstructure and mechanical properties of Fe-Mn-Ni-Cr-Al HEAs.