Microstructure And Properties Of Graphene Reinforced Fe₅₀Mn₃₀Co₁₀Cr₁₀ High-entropy Alloy Composites

As a newly discovered material in the 21st century,graphene has excellent mechanical,electrical and thermodynamic properties and can be used to enhance high-entropy alloys to prepare high-strength composite materials.Based on the reports about the preparation of graphene/high-entropy alloy composites by ball milling,there are no reports on the preparation of graphene/high-entropy alloy composites by ball milling.In this paper,nano-graphene sheets with thickness of 4²0 nm,size of 5¹0?m and layers of less than 20 layers and Fe₅₀Mn₃₀Co₁₀Cr₁₀ high-entropy alloy was prepared by mechanical alloying and spark plasma sintering.The mechanical alloying behavior,the structure,tensile,compression,friction and wear properties of graphene were studied,feasibility of a new generation of aeroengine turbine disk material.In the mechanical alloying process of Fe₅₀Mn₃₀Co₁₀Cr₁₀ high-entropy alloy,the alloying degree increases with increasing milling time,the grain size of the alloy gradually decreases from 31.2 nm to 12.8 nm,and the lattice strain gradually increases from 0.102%to 0.608%,and the average particle size of the alloy powder first decreases and then increases.Scanning electron microscope and X-ray diffractometer tests show that when the ball milling time reaches 50 hours,the Fe,Mn,Co,and Cr elements are evenly distributed and basically proportional;the crystal structure of the alloy powder is a single FCC solid solution,indicating that the powder is completely alloying.After sintered,the composite is still FCC structure solid solution,and a small amount of elemental segregation occurs.The test shows that the density of the composite decreases with the increase of the graphene content,while the hardness of the composite increases first and then decreases with the increase of the graphene.Tensile and compression tests show that changes in graphene content have a significant effect on the properties of the composite.In the tensile test,the yield strength and tensile strength of the composites increase with the increase of the graphene content,but the plasticity decreases;the change trend of the compression test results is approximately the same as the tensile test,and the yield strength and compressive strength increase.However,the plasticity is reduced,but it is worth noting that when the addition amount of graphene reaches 0.4%,the compression property of the material is the best,and the strength and plasticity at this time are improved.Scanning electron microscopy revealed that there were a large number of fine dimples in the tensile fracture of the composite,indicating that the main fracture mechanism of the material is ductile fracture.By electron backscatter diffraction,microstructures of high entropy alloy matrix without graphene were characterized in three different tensile strains of tensile specimens.The results show that the material has a certain recrystallized structure.As the strain increases,the grain of the material also grows.At the same time,the twin crystals in the material also increase.At the same time,in the process of stretching,grain rotation and grain boundary migration occur,which makes the material's low-angle grain boundaries increase.However,the pole figure and the anti-pole diagram show that the grain rotation is not regular,and no obvious preferred orientation is formed.Finally,The stress concentration causes the material to break due to the incoordination of grain movement inside the polycrystalline material.Friction experiments show that the average friction coefficient of Fe₅₀Mn₃₀Co₁₀Cr₁₀ high-entropy alloy is basically the same,when under the load.However,the addition of graphene reduced the average coefficient of friction by 62%to 0.11,but the excess graphene addition had no significant effect on the average coefficient of friction.All four composites have abrasive wear,fagiture wear and oxidation wear,and the three composite materials and the wear-resistant steel balls in the process of grinding material transfer occurred.Besides,Tests show that the wear of high-entropy alloy matrix is very large.When graphene was added,the amount of wear is drastically reduced,making the instrument unable to measure.Experiments show that when the content of graphene is 0.4 wt.%,The high-entropy alloy composite has good compressive properties and excellent anti-friction and wear properties.