Investigation On The Microstructure And Properties Of AlCoCrFeNi Systems High-entropy Alloy Via Laser 3D Printing

Laser 3D printing technology provides a novel technical route for the homogenized investigation of high-entropy alloy complex components,it has the technical advantages of"near net shape",high processing accuracy,high processing flexibility,and high material utilization.High-entropy alloy material with non-equilibrium solidification structure characteristics can directly synthesize.Co Cr Fe Ni as on behalf of the face-centered cubic（FCC）high-entropy alloy with excellent laser three-dimensional forming performance,whereas the Co Cr Fe Ni high-entropy alloy prepared by laser 3D printing displays lower yield strength at ambient temperature.Consequently,improving the comprehensive mechanical properties of FCC-structured high-entropy alloy specimens produced by laser 3D printing has become a research hotspot in this field.Al was gradually added based on the Co Cr Fe Ni high-entropy alloy in this paper,investigating the evolution law for the organization structure and properties of the laser 3D printing Al_xCo Cr Fe Ni-based high-entropy alloy via introducing the hard BCC phase into the alloy structure.Based on this research,the eutectic structure with combination of strength and plasticity was introduced into the alloy structure,and hence Al Co Cr Fe Ni_2.1 eutectic high-entropy alloy material was produced by laser 3D printing technology,investigating on the organization structure and mechanical properties of the laser 3D printing eutectic high-entropy alloy material and compared to that of the corresponding as-cast eutectic high-entropy alloy samples.Investigation on the microstructure and mechanical properties of Al_xCo Cr Fe Ni high-entropy alloy synthesized by laser melting deposition（LMD）technology.The results indicate that the non-equilibrium solidification structure of the Co Cr Fe Ni high-entropy alloy show epitaxially grown coarse columnar crystals under the directional solidification condition.The epitaxially grown grain morphology changes with the addition of Al element,and the non-equilibrium solidification of Al₂₀ alloy exhibits fine columnar crystals and equiaxed crystals;it is observed that the BCC phase preferentially precipitates and grows at the grain and dendrite boundaries in the backscattered electron morphology with the increase of the Al content in the alloy.The alloy organization structure transforms from the FCC structure to the BCC structure.The element distribution diagram indicates that the FCC phase is enriched in Fe,Co,and Cr elements while Al and Ni elements enriched in the BCC phase.The tensile and compressive stress-strain curves display that the Co Cr Fe Ni high-entropy alloy has high ductility while the lower yield strength.Improve in the yield strength and fracture strength of the alloy gradually whereas the ductility continues to decrease accompanying with the continuously increase of Al content.Investigation on the microstructure and mechanical properties of Al Co Cr Fe Ni_2.1eutectic high-entropy alloy synthesized by laser melting deposition technology.The results exhibit that the Al Co Cr Fe Ni_2.1 eutectic high-entropy alloy possesses excellent laser 3D printing formability.The produced alloy specimen shows metallic luster and without overt defects on the surface and it microstructure is consisted of dual-phase（FCC+B2）lamellar eutectic structure with alternately distributing and accompanying growth;the LMD sample possesses a more uniform and fine lamellar eutectic structure（the thickness of the cast sample is roughly 1～3μm,and the thickness of the LMD sample is around 0.5～1.5μm）compared to that of the corresponding cast specimens;On the basis of this unique microstructure,exhibiting the high strength and high plasticity for the comprehensive tensile mechanical properties of Al Co Cr Fe Ni_2.1 eutectic high-entropy alloy owing to the fact that FCC/B2 semi-coherent phase boundary can enable a part of dislocations generate the pinning effect and another part of the dislocations can continue to be delivered to the B2 phase via the phase boundary during the deformation.The LMD specimens possesses a finer eutectic structure than the corresponding cast,hence it should be noted that more semi-coherent phase boundaries per unit area were contained.As a result,simultaneously enhancement in the tensile strength and fracture elongation of the Al Co Cr Fe Ni_2.1 eutectic high-entropy alloy.In conclusion,Al Co Cr Fe Ni high-entropy alloy specimens have been successfully synthesized via laser melting deposition technology in this study,and the microstructure and mechanical of this alloy specimens were systematically investigated.Consequently,providing a novel ways and technical routes for producing high entropy alloys with high strength and high plasticity.