Manipulating A2/B2 microstructure via adjusting Al/Ni ratio in cost-effective Fe-based AlNiFeCr alloys for controllable strength-plasticity combination

Cost-effective Fe-based Al-Cr-Fe-Ni alloys were prepared by arc melting process, and Al/Ni ratio in AlxNi(40-x)Fe40Cr20 (0 ≤ x ≤ 40, at.%) alloy was adjusted for superior mechanical properties. With increasing x, the initial FCC phase diminishes and A2/B2 phase is promoted. Two typical A2/B2 structures are observed, one consists of spherical/cuboidal B2 nanoparticles distributed in A2 matrix (denoted as AMBP), and the other consists of ellipsoidal and plate-like A2 particles distributed in B2 matrix (denoted as BMAP). The fraction of AMBP domains decreases while that of BMAP increases with increasing x, which is harder with lowered plasticity/toughness, accompanied with some micro-cracks propagating along the plate-like A2/B2 interfaces in BMAP domains. The alloy shows the best strength-plasticity combination at x = 15 with >95 vol% AMBP domains. This study suggests a cost-effective Al15Ni25Fe40Cr20 medium- entropy alloy with superior strength-plasticity combination. The Al15Ni25Fe40Cr20 alloy per metric ton is 13% and 18% cheaper than well-known equiatomic AlCrFeNi alloy and AlCrFe2Ni2 alloy, respectively.