Microstructure And Properties Of AlCoCrFeNiCu_x High-entropy Alloy Fabricated By Laser Additive Manufacturing

The synergy of multiple elements allows high-entropy alloys to have many excellent properties at the same time.The high-entropy alloys currently studied are mostly prepared by vacuum arc or induction melting.The properties of the alloy are determined by the chemical composition and the structure of the structure,but the preparation method directly affects the microstructure of the alloy and thus affects the mechanical properties.Additive manufacturing has the advantages of no need for mold,complicated structure and high material utilization.Many traditional alloys can be formed by additive manufacturing technology.Therefore,the additive preparation technology of high-entropy alloy is studied in this paper.Laser selective melting and forming studies were carried out by selecting Al_0.3CoCrCuFeNi and AlCoCrFeNi_2.1.1 high-entropy alloys with excellent as-cast properties.AlCoCrFeNi_2.1.1 high-entropy alloy has the lowest sample defects and the density exceeds the as-cast state under the appropriate SLM process parameters?laser power 130w,scanning speed 1000mm/s,thickness of 0.04mm?.For the Al_0.3CoCrCuFeNi high-entropy alloy,due to the low melting point Cu element,the segregation of Cu element in the laser melting forming experiment promotes the generation of cracks,and the existence of microcracks can always be observed in the prepared samples.Microstructure analysis of AlCoCrFeNi_2.1.1 high-entropy alloy SLMed samples:under high-power scanning electron microscopy,the as-cast layered eutectic structure with a layer spacing of about 2?m;and the SLMed sample is a cellular substructure eutectic structure,size between 200nm¹000nm.After the additive manufacturing,the element distribution is more uniform and the microstructure is finer,indicating that the cooling rate and preparation method have a significant influence on the microstructure of the alloy.Compared with the as-cast AlCoCrFeNi_2.1.1 high-entropy alloy,the SLMed specimen has a significant improvement in strength and plasticity.The yield strength is increased from 545MPa to 1040 MPa,the tensile strength is increased from 1070 MPa to 1200 MPa,and the fracture plasticity is increased from 17%to 23%,the hardness is increased from 320HV to354HV.The wear mechanism of the SLMed specimen is mainly adhesive wear;the wear state of the as-cast specimen is due to the presence of the hard B2 phase,and the wear mechanism is adhesive wear accompanied by abrasive wear.The wear resistance of the as-cast sample is better than that of the SLMed sample.In the corrosive environment of 3.5wt%NaCl solution,the corrosion resistance of as-cast AlCoCrFeNi_2.1.1 high-entropy alloy is comparable to that of 304 stainless steel.The corrosion resistance of AlCoCrFeNi_2.1.1 high-entropy alloy prepared by SLM is almost the same as that of as-cast.The method has almost no effect on corrosion resistance.