Microsturcture Control And Properities Study Of AlCoCrFeNi_2.1 Eutectic High-entropy Alloy

AlCoCrFeNi_2.1eutectic high-entropy alloy（EHEA）is a high entropy alloy with great potential for industrial application due to its excellent strength-plasticity ratio and good castability,and has received a lot of attention from researchers.has good strength-plasticity ratio and good castability,which is expected to achieve industrial applications and has been widely studied by researchers.In this thesis,the microstructure of AlCoCrFeNi_2.1EHEA was changed by using laser surface remelting technique,warm rolling and annealing treatment,and C-gap solution strengthening,and the hardness,wear resistance,corrosion resistance and tensile properties were analyzed,and the main conclusions are as follows:（1）No new phases were generated in the remelted layer after laser remelting,which were all composed of FCC and BCC phases.The cast AlCoCrFeNi_2.1high entropy alloy（HEA）has a lamellar spacing of 4μm and a hardness of 293 HV,while the laser surface remelting of AlCoCrFeNi_2.1HEA has a significantly finer lamellar structure of only 0.476μm and an increased hardness of 351 HV.The corrosion resistance was significantly enhanced in 3.5 wt.%Na Cl solution,with self-corrosion potential and self-corrosion current density of-308 m V and 1.362×10^-7A·cm^-2.The improved corrosion resistance of the remelted layer was attributed to the improvement of the stability of the passivation film due to the obvious refinement of the BCC phase as the anode site and the relatively uniform distribution of the elements.（2）After the warm rolling treatment,the regular layer lamellar eutectic tissue was bent and deformed by strong external forces during the rolling process,and some of the tissues were fractured and obvious grain boundaries appeared inside the tissues.The hardness of the as-cast AlCoCrFeNi_2.1HEA is 293 HV,and the hardness of the rolled HEA is the largest,about 496 HV,which gradually decreases with the increase of the annealing temperature,and the hardness of the annealed AlCoCrFeNi_2.1high-entropy alloy gold at 800℃decreases to 363 HV.The wear of the annealed AlCoCrFeNi_2.1HEA at 700℃is the smallest,only 0.0145 mm³.In addition,it is found that the corrosion resistance of the coarse labyrinth-like organization is less than that of the fine lamellar eutectic organization.（3）The microstructure of(AlCoCrFeNi_2.1)₉₉C₁HEA consists of regular lamellar eutectic and dissociated eutectic,with white granular and needle-like carbides precipitated along the grain boundaries,and the carbide size is about 0.5-5μm.After the solid solution treatment at 1150℃for 20 min,the carbide is obviously re-soluble,and the volume fraction of carbide decreases and the size of carbide decreases significantly.The hardness of(AlCoCrFeNi_2.1)₉₉C₁HEA is 301 HV higher than that of cast AlCoCrFeNi_2.1HEA 280 HV,and the wear volume of(AlCoCrFeNi_2.1)₉₉C₁HEA is 0.0148 mm³compared with that of cast AlCoCrFeNi_2.1HEA.Compared to the as-cast HEA,its wear volume decreased by 24.1%.The(AlCoCrFeNi_2.1)₉₉C₁-20 HEA has good room temperature tensile properties with yield strength of 431.4 MPa,tensile fracture strength of 1047.4 MPa,and elongation of 17.6%.