A cost-effective iron-rich medium entropy alloys with the balance of strength and ductility

Abstract

Iron-rich medium-entropy alloys (MEAs) have attracted attention due to the balance for cost and properties of alloy. In this study, a combined metastability engineering and eutectic high-entropy alloys (EHEAs) design strategy were employed to develop a cost-effective, iron-rich MEAs for the Fe–Cr–Ni–Al MEAs system using CALPHAD simulations. This approach enabled the tailored control of soft and hard phases within the non-isoatomic MEAs system by manipulating the elemental ratios. Specifically, increasing the aluminum (Al) content promoted the stability of the BCC/B2 phase, and the microstructure of the MEA transitioned from a single-phase FCC structure to a mixed FCC + BCC/B2 structure, culminating in a final single-phase BCC/B2 structure. This BCC/B2 phase precipitation strengthening mechanism led to enhanced microhardness and yield strength in MEAs with high Al content. Notably, the Al11-as alloy demonstrated a yield strength of 692.7 ± 30.4 MPa (precipitation strengthening is ∼428.98 MPa, accounting for the true yield strength of the alloy ∼61.9 %), with an ultimate tensile strength reaching a maximum value of 992.3 ± 32.77 MPa. Moreover, the alloy retained a satisfactory elongation of 7.1 ± 2.9 %. These efforts hold promise for the development and application of cost-effective, iron-rich MEAs for the Fe–Cr–Ni–Al MEAs system.