Improving mechanical properties of an additively manufactured high-entropy alloy via post thermomechanical treatment

Abstract

Thermomechanical treatment is applied to a CrMnFeCoNi high-entropy alloy fabricated via laser melting deposition (LMD) with 5 wt% WC addition to improve its mechanical properties. After the thermomechanical treatment, the yield strength of the LMD-fabricated alloy increases by 323 MPa, while the elongation remains nearly unchanged. Microstructures of the alloy before and after the thermomechanical treatment are thoroughly characterized. The LMD-fabricated alloy consists of the face-centered cubic matrix and M23C6 precipitates distributed both at grain boundaries and within matrix grains. The thermomechanical treatment leads to a significant refinement of the matrix grains and a more uniform distribution of the M23C6 precipitates, and largely these two factors give rise to the increase in yield strength. Numerous dislocations induced by internal thermal stress due to LMD are effectively eliminated through the thermomechanical treatment, contributing to the preservation of the ductility. The M23C6 carbide precipitates are characterized regarding their spatial distribution, chemical composition, and stacking faults, along with the orientation relationship and the interfaces between the matrix and the precipitates.