A Si-containing FeCoCrNi high-entropy alloy with high strength and ductility synthesized in situ via selective laser melting

Abstract

To widen the applications of new materials in additive manufacturing (AM), the traditional method of printing using pre-alloyed powders should be improved because the pre-alloying process is expensive and makes it difficult to adjust the composition of new materials. This study investigates the synthesis of a FeCoCrNi high-entropy alloy (HEA) containing 1.5 at.% Si in situ using selective laser melting (SLM). A remelting strategy and process optimization based on polynomial regression modeling allowed for the printing of almost fully dense (99.78 %) samples. The samples comprised columnar grains, each containing numerous subgrains of a single-phase face-centered cubic solid solution. No precipitation or segregation were observed. The room temperature tensile properties of the samples were excellent, with yields and tensile strengths reaching 701 ± 14 and 907 ± 25 MPa, respectively, and an elongation at fracture of 30.8 ± 2%. These properties were attributed to solid solution strengthening and novel dislocation loop strengthening mechanism. These findings demonstrate that HEAs with a high relative density and good mechanical properties can be directly synthesized by SLM using inexpensive pure metal powders, thereby extending the application potential of AM to manufacture new materials.