Phase Transition Mechanism and Mechanical Properties of AlCrFe2Ni2 High-Entropy Alloys with Changes in the Applied Carbon Content

To understand the effect of carbon addition on dual-phase high-entropy alloys (HEAs), the mechanism of phase transition and mechanical properties of AlCrFe2Ni2Cx (x = 0, 0.06, 0.12, 0.18, 0.24) are investigated systematically. The results show that carbon addition induced the growth and aggregate of disordered noodle-like face-centered cubic (FCC) phases. The volume fraction of the FCC phase increases from 33.2% to 51.2% as the C content increases. The Al and Ni in the alloys are segregated at the phase boundaries. Disappearance of the spinodal decomposition structure compose of a disordered body-centered cubic (BCC) structure and an ordered BCC structure (B2). The BCC phase transform into a spherical B2 phase with increasing C content. The experimental mechanical properties show that the yield strength of the HEAs is closely related to the volume fraction of BCC phase as the C content increases. The epsilon phase (Cr, C carbonization) precipitate in an FCC phase when the C content is above 2.0 at%. The hardness of the HEAs increases from 310 to 357 HV as the C content increases. The compressive strength and the fracture strain of the alloy decreases as the C content increases.