A combinatorial assessment of microstructure and mechanical properties in AlCrCuFeNi₂V_x concentrated alloys

This study developed a novel series of AlCrCuFeNi₂V_x (x = 0, 0.3 and 0.6) high-entropy alloys (HEAs), and systemically assessed the relationship between composition, processing, microstructure and mechanical properties. The alloys were produced by arc melting and studied in as-solidified and homogenized (annealing at 650 ℃ for 4 h) conditions. In the base alloy of AlCrCuFeNi₂, the microstructure consists of disordered bcc and fcc phases, ordered B2 and L1₂ phases, and the B2 phase and bcc phase are coherent. With the increase of V content, the volume fraction of bcc/B2 phases increase, accompanied with a peculiar phenomenon that the shape of B2 phase has transferred from irregular matrix to spherical precipitates, which caused by the increase of lattice misfit after V addition. Moreover, a large number of Cu particles are randomly distributed in the NiAl (B2) phase, and the crystal structure of Cu particles has changed from 9 R structure to fcc structure after annealing treatment. Mechanical tests of these alloys reveal that the 0.6 at% V addition has doubled the yield strength (V0, 780 MPa; V0.6, 1673 MPa) for the increase in volume fraction of bcc/B2 phase and the solid solution strengthening produces by V addition. The yield strength is increased by 124 MPa after annealing treatment in V0.6 alloy without sacrificing the ductility due to the promotion of L1₂ phase after annealing treatment.