Tailoring the microstructure through laser processing parameters for property optimization of a high-entropy alloy fabricated by laser powder bed fusion

Abstract

Laser powder bed fusion (LPBF) offers a promising route to high-entropy alloys (HEAs) with refined microstructures. Here the individual roles of laser power and scanning speed in governing the densification, microstructure, and tensile behavior of FeNiCrCo HEA are systematically examined, with particular attention to effects that go beyond the volumetric energy density (VED) descriptor. Through orthogonal experiments (laser power: 80–160 W, scanning speed: 400–1200 mm/s), the optimal processing window was identified at 160 W and 400 mm/s, achieving a relative density exceeding 99.8%. The as-built alloy exhibits a single-phase face-centered cubic (FCC) structure with homogeneous elemental distribution, consisting of columnar grains with subgrain boundaries composed of dense dislocation networks. Notably, laser power and scanning speed exert differentiated effects that VED alone cannot fully capture: increasing laser power promotes the formation of low-angle grain boundaries and enhances texture intensity, while varying scanning speed produces distinct effects on grain morphology and dislocation density. The ultimate tensile strength ranges from 596 to 635 MPa, increasing with laser power but decreasing with scanning speed, whereas the total elongation remains near 33 ± 4% for all conditions. This study establishes that decoupling laser power and scanning speed effects is essential for precise microstructural control in LPBF-fabricated HEAs.