3D printing of fine-grained aluminum alloys through extrusion-based additive manufacturing:Microstructure and property characterization

Additive manufacturing(AM)has the potential to transform manufacturing by enabling previously un-thinkable products,digital inventory and delivery,and distributed manufacturing.Here we presented an extrusion-based metal AM method(refer to“SoftTouch”depositionin thefiledpatent)thatis suitablefor making the metal feedstock flowable prior to the deposition through dynamic recrystallization induced grain refinement at elevated temperatures.The flowable metal was extruded out of the printer head like a paste for building dense metal parts with fine equiaxed grains and wrought mechanical properties.Off-the-shelf metal rods were used as feedstock and the printing process was completed in an open-air environment,avoiding pricy powders and costly inert or vacuum conditions.The resulting multi-layer de-posited 6061 aluminum alloys yield strength and ductility comparable to wrought 6061 aluminum alloys after the same T6 heat treatment.The extrusion-based metal AM method can also be advanced as green manufacturing technologies for fabricating novel alloys and composites,adding novel features to existing parts,repairing damaged metal parts,and welding advanced metals for supporting sustainable manufac-turing,in addition to being developed into a cost-effective manufacturing process for the fabrication of dense metal of complex structural forms.

Dual-phase synergistic deformation characteristics and strengthening mechanism of AlCoCrFeNi_(2.1) eutectic high entropy alloy fabricated by laser powder bed fusion

Eutectic high entropy alloy(EHEA)possesses promising prospects for industrial application due to its controllable and near-equilibrium dual-phase structure.Due to the advantages of high material utiliza-tion,efficient production,and design freedom,the laser powder bed fusion(LPBF)technique provides a new path to prepare EHEA components with complex structure and excellent performance.In this study,near fully dense AlCoCrFeNi_(2.1) samples were obtained by adjusting the process parameters of LPBF.Con-sidering the balling phenomenon and powder splashing during the LPBF process,laser remelting was selected as an optimized scanning strategy to further improve the forming quality of AlCoCrFeNi21.The microstructure of remelted AlCoCrFeNi_(2.1) sample exhibited regular eutectic lamellae consisting of nano-scale face-centered-cubic(FCC)and B2 phases,in which the FCC phase accounted for a higher proportion.By investigating the tensile behavior and deformation mechanism,it was revealed that the ultrafine eu-tectic lamellae could induce a strong dual-phase synergistic strengthening,thereby significantly improv-ing the strength of the sample.Compared with the vacuum induction melted(VIM)sample,the remelted sample showed a 54%increase in ultimate tensile strength(UTS-1518 MPa)and a 130%increase in yield strength(YS-1235 MPa)with reasonable plasticity.This study indicates that by combining the design and manufacturing freedom of LPBF with the EHEA,it is expected to fabricate high-property 3D EHEA parts,expanding the application field of EHEA.