Microstructures and properties of CrxFeNi(3-x)Al high-entropy alloys.

A set of novel Co-free high-entropy alloys CrxFeNi(3-x)Al (x = 0.25, 0.5, 0.75, 1, 1.25, 1.5) were fabricated by non-self-consumable vacuum melting method, and their solidification microstructures as well as compression properties were investigated. The research results firstly demonstrate that the solidification microstructures of Cr-0.25, Cr-0.5 and Cr-0.75 are composed of primary B2 phase and (FCC + B2) eutectic structure; Secondly, there are primary B2 phase and (FCC + B2) eutectic structure in the solidification microstructure of Cr-1, with a tiny amount of BCC phase distributing on the matrix of primary phase B2; In addition, as a "sunflower-like" structure of BCC phase and B2 phase, the solidification microstructure of Cr-1.25 is identified. Also, the core of the sunflower is B2 phase, and the petals are alternately arranged by BCC phase and B2 phase; Last but not least, it is a fine BCC phase and B2 dual-phase structure that form the solidification microstructure of Cr-1.5. Among the phases mentioned above, the FCC phase is abundant in Ni and Fe elements, the B2 phase is abundant in Ni and Al elements, and the BCC phase is abundant in Cr element. With the ascending trend of Cr content, the strength of CrxFeNi(3-x)Al high-entropy alloy descends initially and then climbs, during which the primary reasons for the rise of strength are solid solution strengthening, fine crystal strengthening and precipitation of BCC phase. The compressive strengths of Cr-1.25 and Cr-1.5 alloys are 2111.5 and 1985.3 MPa, respectively, and the compressibility can attain to 41.36 and 49.87%, respectively, manifesting comprehensive mechanical properties. [ABSTRACT FROM AUTHOR]