Microstructure and Nanoindentation Behavior of FeCoNiAlTi High-Entropy Alloy-Reinforced 316L Stainless Steel Composite Fabricated by Selective Laser Melting.

Selective laser melting (SLM) is one of the metal additive manufactured technologies with the highest forming precision, which prepares metal components through melting powders layer by layer with a high-energy laser beam. The 316L stainless steel is widely used due to its excellent formability and corrosion resistance. However, its low hardness limits its further application. Therefore, researchers are committed to improving the hardness of stainless steel by adding reinforcement to stainless steel matrix to fabricate composites. Traditional reinforcement comprises rigid ceramic particles, such as carbides and oxides, while the research on high entropy alloys as reinforcement is limited. In this study, characterisation by appropriate methods, inductively coupled plasma, microscopy and nanointendation assay, showed that we successfully prepared the FeCoNiAlTi high entropy alloy (HEA)-reinforced 316L stainless steel composites using SLM. When the reinforcement ratio is 2 wt.%, the composite samples show higher density. The SLM-fabricated 316L stainless steel displays columnar grains and it varies to equiaxed grains in composites reinforced with 2 wt.% FeCoNiAlTi HEA. The grain size decreases drastically, and the percentage of the low angle grain boundary in the composite is much higher than in the 316L stainless steel matrix. The nanohardness of the composite reinforced with 2 wt.% FeCoNiAlTi HEA is twice as high as the 316L stainless steel matrix. This work demonstrates the feasibility of using a high-entropy alloy as potential reinforcement in stainless steel systems.