Selective Laser Melting (SLM) Additively Manufactured CoCrFeNiMn High-Entropy Alloy: Process Optimization, Microscale Mechanical Mechanism, and High-Cycle Fatigue Behavior

Abstract

The equiatomic CoCrFeNiMn high-entropy alloy (HEA) possesses excellent properties including exceptional strength–ductility synergy, high corrosion resistance, and good thermal stability. Selective laser melting (SLM) additive manufacturing facilitates the convenient fabrication of the CoCrFeNiMn HEA parts with complex geometries. Here, the SLM process optimization was conducted to achieve a high relative density of as-built CoCrFeNiMn HEA bulks. The mechanisms of process-induced defects and process control were elucidated. The microscale mechanical behaviors were analyzed through in situ scanning electron microscopy observation during the compression tests on micro-pillars of the as-built HEA. The stress–strain characteristics by repeated slip and mechanism of “dislocation avalanche” during the compression of micro-pillars were discussed. The high-cycle fatigue tests of the as-built HEA were performed. It was found that a large number of nano-twins were induced by the fatigue, causing a non-negligible cycle softening phenomenon. The effects of promoted ductility due to the fatigue-induced nano-twins were illustrated. This work has some significance for the engineering application of the SLM additively manufactured CoCrFeNiMn HEA parts.

Deformation Behavior of 3D‐Printed High‐Entropy Alloys: A Critical Review

“…[ 173 ] High‐density nanotwins were also observed after the stress‐controlled fatigue of SLM‐fabricated CrMnFeCoNi HEA. [ 224 ] Apart from fatigue‐induced twinning, the LPBF‐fabricated Fe 40 Mn 20 Co 20 Cr 15 Si 5 HEA also showed fatigue‐induced FCC‐to‐HCP transformation due to low stacking fault energy. The deformation twinning in the transformed HCP phase further enhanced the fatigue limit to 325 MPa in the stress‐controlled fully‐reversed bending fatigue tests.…”

Interfacial Characterization of Selective Laser Melting of a SS316L/NiTi Multi-Material with a High-Entropy Alloy Interlayer

“…During the fabrication of the multi-material 316L/HEA/NiTi samples via SLM, the HEA alloy was built onto the 316L alloy, followed by the NiTi alloy onto the HEA. HEA samples were successfully obtained via SLM, and the energy density for this alloy was selected on the basis of this study [23]. For 316L and HEA alloys, the SLM parameters were chosen based on energy density according to existing data [24,25].…”

Effects of Selective Laser Melting Process Parameters on Structural, Mechanical, Tribological and Corrosion Properties of CoCrFeMnNi High Entropy Alloy

“…Zhang et al [27] utilized different screening strategies to optimize the process parameters of CoCrFeNiMn HEA produced by SLM. They observed that increasing laser energy density initially led to higher sample density (up to 98.87%), but further energy increases resulted in decreased density, eventually stabilizing.…”