Influence of molten pool evolution on crystalline features and mechanical performance of CoCrFeMnNi high-entropy alloys during laser powder bed fusion

• The molten pool evolution under varied laser construction angles, and its influence on the crystalline features and mechanical performance of CoCrFeMnNi high-entropy alloys is validated. • The similar molten pool morphology can be formed in the side working planes of the as-printed alloys by inclining the construction angle. • The epitaxial growth of columnar grain is interrupted by decreasing the heat dissipation rate and enlarging the horizontal-section proportion of molten pool. • The trade-off strength-ductility performance is achieved, via governing the strengthening mechanisms and fracture behaviors. The crystallization behaviors critically influence the mechanical performance of alloy parts. Especially in widely-concerned additive manufacturing process, the anisotropic microstructure with coarse columnar grains is easily formed to deteriorate service performance. By the reason that the crystallization process is closely related to the heat transmission of molten pool, adjusting construction angle will be an effective way for mechanical performance regulation. This work studies the molten pool evolution of CoCrFeMnNi high-entropy alloys (HEAs) under different construction angles during laser powder bed fusion, and its contributions to the crystalline features and mechanical performance. Compared to regular construction form (0°/90°), the HEAs under 45° show the improved tensile strength to about 24 %, and maintain a high elongation rate of 31 %. Through systematic characterization, it can be obtained that only adopting the widely-known interlayer rotation strategy still results in coarse columnar grains growth in solid-solution HEAs. Whereas, integrating construction angle regulation could promote equiaxed grains formation and interrupt epitaxial growth of columnar grains, by decreasing the heat dissipation rate and enlarging horizontal-section proportion of molten pool in the working planes. Thereby, the strengthening mechanisms (grain-boundary and dislocation strengthening) and fracture behaviors (microcrack/pore propagation) are ameliorated to achieve the trade-off strength-ductility performance.