Understanding elemental distribution in Cu/Mo-added Fe2Ni2CrMn high-entropy alloys processed by laser powder bed fusion

This study investigates the micro- and nano-segregation, and the cracking behavior of a non-equimolar face-centered cubic (FCC) (Fe₂Ni₂CrMn)₉₀ + (Mo₃Cu₇)₁₀ High Entropy Alloy (HEA) produced by Laser Powder Bed Fusion (LPBF). It evaluates how varying the printing parameters, specifically the laser power and scanning speed, affects the alloy’s microstructure and elemental distribution. The experimental findings demonstrate that changes in the Volumetric Energy Density (VED) significantly influence the Mn and Cu segregation. At higher VEDs, lower cooling rates enable near-equilibrium solidification, promoting the Mn and Cu co-segregation at high angle grain boundaries (HAGB), with Cu displaying more pronounced discontinuous patterns. Conversely, lower VEDs, associated with higher cooling rates, induce solute trapping, leading to segregation primarily located at the melt pool boundaries, with Mn concentrated within the solidified melt pool regions. This phenomenon could be compatible with the vaporization of Mn. Nanoscale analysis using a scanning transmission electron microscope (STEM) equipped with a high-angle annular dark-field (HAADF) detector further confirmed that Mn and Cu form distinct layers at cell walls, regardless of the printing parameters employed. Scheil simulations supported these experimental results, predicting that elements like Mn and Cu, which have partition coefficients (k) lower than one, preferentially remain in the liquid phase during solidification. This behavior leads to their enrichment in the residual liquid, promoting segregation in the last stages of solidification. In addition, the role of the segregation in the crack propagation has a minor influence. While solidification and solid-state cracking were visible in all conditions, liquation cracking occurred only at the highest VED. This suggests that the shrinkage during solidification and the residual stresses in the solidified material are the primary cause of cracking. • Cu and Mn segregation patterns are strongly dependent on LPBF printing parameters. • High VED promotes Mn–Cu co-segregation at high-angle grain boundaries. • Low VED induces Mn segregation within melt pools. • Cellular segregation remains consistent across all conditions, matching Scheil simulations. • Cracking is dominated by residual stress, not segregation, except at highest VED.