Improved passivation ability via tuning dislocation cell substructures for FeCoCrNiMn high-entropy alloy fabricated by laser powder bed fusion

Elemental-decorated dislocation cell is a specific substructure in additively manufactured metals and alloys due to the intrinsic layer-by-layer rapid melting and solidification process, and the novel cellular structures would have significant influences on the service performances of the printed components. In this work, sub-micro Mn-decorated dislocation cells are verified in FeCoCrNiMn high-entropy alloys (HEAs) fabricated via laser powder bed fusion (L-PBF), and the related passivation capabilities are comparably investigated with the as-casted and heat-treated L-PBF counterparts (HEA-800, 800 °C for 2 h). The passive current density of L-PBF HEA-800 is the lowest in borate buffer solutions, while the as-casted HEAs show the highest corrosion rate therein. The high-density dislocation and the alleviation of Mn segregation at the cellular boundaries are conducive to the superior protectiveness (stable and thick passive film) for L-PBF HEA-800 and the underlying mechanisms for different passivation behaviors are discussed.