Anomalous microstructure and excellent mechanical properties of Ni35Al21.67Cr21.67Fe21.67 high-entropy alloy with BCC and B2 structure

A quarternary Co-free Ni35Al21.67Cr21.67Fe21.67 high entropy alloy was designed and prepared by arc melting. The Ni35Al21.67Cr21.67Fe21.67 high entropy alloy (HEA) possesses disordered BCC phase and ordered BCC phase (B2). A “sunflower-like” microstructure was found in Ni35Al21.67Cr21.67Fe21.67 high entropy alloy. B2 phase forms the continuous matrix with the disordered BCC spherical particles (200 nm-300 nm) in 'core' region. In 'petal' region, striped B2 phases are inlaid in disordered BCC matrix. Moreover, the result of mechanical property test suggests that alloy presents outstanding compressive strength and excellent ductility with the microstructure of B2/BCC phase. The alloy showed an excellent comprehensive properties at room temperature (yield strength σ0.2 = 1471 MPa, compressive strength σb = 3541 MPa and compression rate ε = 40%) , which was superior to some traditional metallic materials. High strength was mainly attributed to high volume fraction of hard B2 phase matrix and B2 precipitations strengthening. Dislocations motion in disordered BCC matrix provided ductility for the alloy. The Ni35Al21.67Cr21.67Fe21.67 HEA has promising use in future structural applications.