Investigation of correlation between the microstructural characteristics and mechanical properties of (CoCuFeNi)100-xAlx high entropy alloys

Abstract

In the present study, we investigated the Al effect on the microstructure, phase, and mechanical properties of (CoCuFeNi)100-xAlx (x = 0 ∼ 20 at%) high entropy alloys (HEAs). To find out the correlation between the microstructural characterization and mechanical properties, a detailed phase and microstructural analysis was conducted through slight addition of the Al content. From Al0 to Al15 HEAs, there was no distinct change in dendritic microstructural morphology and mechanical properties. On the other hand, the B2 phase appears in the inter-dendrite region and thus (FCC1 +FCC2 +B2) multi-phase formed showing the conspicuous mechanical properties from Al15 to Al20 HEAs. Especially, Al18 HEA showed the most balanced mechanical properties due to the two-sided microstructure of (FCC+L12 +B2) and (B2 +FCC/L12). However, it was identified that the excessive Al content formed the primary B2 dendrite changing ductile to brittle deformation mode. The phase and microstructure analysis was conducted by multi-scale XRD, SEM, and TEM. Furthermore, systematic deformation mechanical analysis was carried out on deformed and fractured specimens.