Additive manufacturing of fine-grained and dislocation-populated CrMnFeCoNi high entropy alloy by laser engineered net shaping

The equiatomic CrMnFeCoNi high entropy alloy is additively manufactured by the laser engineered net shaping (LENS (TM)) process, and the solidification conditions, phase formation, as-deposited microstructures, and tensile behavior are investigated. The LENS (TM)-deposited CrMnFeCoNi alloy exhibits a single-phase disordered face centered cubic (FCC) structure, as evidenced by X-ray diffraction (XRD), and rationalized by Scheil's solidification simulation. Furthermore, microstructures at multiple length scales, i.e. columnar grains, solidification substructures, and dislocation substructures, are formed. The tensile deformation process is mainly accommodated by dislocation activities with the assistance of deformation twinning. The tensile yield strength of the LENS (TM)-deposited CrMnFeCoNi alloy is comparable to that of finer-grained wrought-annealed counterparts, due to the additional initial-dislocation strengthening. However, the uniform tensile elongation, by contrast, is lowered, which is attributed to the increased dynamic dislocation recovery rate and hence the weakened work hardening capability of the LENS (TM)-deposited CrMnFeCoNi. This study demonstrates the capability of the LENS (TM) process for manufacturing the CrMnFeCoNi alloy, with high performance, for engineering applications.