Preparation And Properties Research Of Al-Co-Cr-Cu-Fe-Ni Multiprincipal Alloys Powders

High-entropy alloys（HEAs）are composed of five or more principal elements at equimolar or near-equimolar ratios,and the concentration of each element is between 5³5 at%.The structure of the HEAs typically consists of simple face-centered cubic（FCC）,body-centered cubic（BCC）,hexagonal closed-packed（HCP）solid solution phases,and a mix of FCC,BCC,or HCP,rather than intermetallic compounds and other complex structures.Now,the entirely new alloy field has stimulated great interest because of their novel physicochemical properties such as high ductility and strength,excellence wear resistance,outstanding corrosion resistance,and superior high temperature stability.In this paper,Al-Co-Cr-Cu-Fe-Ni system multicomponent alloy powder were prepared by atomization one-step method,plasma arc method and thermite process.The microstructure and chemical composition of the nanoparticles were characterized by X-ray diffraction（XRD）,scanning electron microscope with X-ray energy spectrum（SEM-EDS）,transmission electron microscope with X-ray energy spectrum（TEM-EDS）and inductive coupled plasma atomic emission spectroscopy（ICP-AES）,and the corrosion resistance and magnetic properties were also investigated.Firstly,The Al CoCrFeNi_2.1.1 powder was prepared by one-step gas atomization method using the purity of 99.0 wt%of Al,Co,Cr,Fe,and Ni as raw materials.The results show that the as-atomized AlCoCrFeNi_2.1.1 nanoparticles possess a fine dual-phase microstructure of FCC and BCC phase,and have spherical shape with a homogeneous composition,and the particles size is 20-80μm.Compared with 304L stainless steel powder,the AlCoCrFe Ni_2.1.1 powder exhibits excellence corrosion resistance in both 10%HCl and 3.5 wt%NaCl solution,and the corrosion current density is reduced by 61.64%and 7.49%,respectively.The magnetic property of AlCoCrFeNi_2.1.1 powder is a typical soft magnetic material.Secondly,the Al-Co-Cr-Cu-Fe-Ni nanoparticles were prepared by modified arc-discharge method using the purity of 99.0 wt%Al,Co,Cr,Fe,and Ni as raw materials.The results show that the evolution of phase structure changes from the initial single Cu-rich FCC to FCC+M₃Al-type L1₂ phases,and eventually to FCC+BCC phase with increasing Al contents.Moreover,the as-prepared nanoparticles are spherical with an average size of about 110-180 nm.Furthermore,the corrosion resistance deteriorates and the soft magnetic behavior increases,when the structure changes from the simple FCC phase to a mixture of FCC and BCC phase.The emergence of M₃Al type L1₂ phase in the FCC matrix brings the best corrosion resistance and the lowest soft magnetic property.Finally,the multiprincipal alloys nanoparticles were prepared by aluminothermic reduction,using Al as reducing agent and metal chloride（CoCl₂·6H₂O,CrCl₃·6H₂O,CuCl₂·2H₂O,FeCl₃·6H₂O,NiCl₂·6H₂O）as oxidants.On the basis of CoFeNi alloy nanoparticles,other six kinds of multi-priary alloy nanopowders,which by replacing or adding Cu and Cr,were prepared by aluminothermic reduction.The results show that the six nanoparticles all possess a FCC phase,and have spherical shape with a homogeneous composition.The results indicate that the corrosion resistances were all improved when Cu substituted one of the element of CoFeNi ternary nanoparticles in either 10%HCl or3.5 wt%NaCl solution,and the order of the corrosion resistance of the ternary nanoparticles was in that CuFeNi>CoCuFe>CoCuNi>CoFe Ni.When Cu or Cu and Cr elements were introduced to the CoFeNi nanoparticles,the corrosion resistances were also increased,and the order of the corrosion resistance of the multiprincipal nanoparticles was as follows:CoCrCuFeNi>CoCuFeNi>CoFeNi.The magnetic property of nanoparticles were soft magnetic material,and the addition of elements Cu and Cr reduced Ms and improved.