| Particle-reinforced aluminum matrix composites are widely used in modern engineering with good specific strength and stiffness.However,as engineering applications have evolved,the properties of composites no longer meet the requirements,particularly in terms of surface properties.Laser cladding technology is the first choice for surface modification of materials due to its high degree of automation,good mechanical repeatability,and good coating quality.Due to high entropy alloys have a thermodynamic high entropy effect,lattice distortion effect,and five other effects,making them unique in terms of wear resistance,corrosion resistance,and other advantages.In this work,in-situ Zr B2/AA6111 aluminum matrix composites were prepared,and the interfacial structure of the reinforcing phase and matrix,the wear properties and wear mechanism of the composites was investigated,and a wear mechanism model was established.Laser cladding technology is used to clad the surface of the composites with a mixed powder of five metal monomers,alloyed and metallurgically bonded to the matrix under the laser photo-thermal conversion effect,resulting in the formation of a Fe Cu Mo Ti V high-entropy alloy coating.The microstructure and properties of the coating were used to select the optimum laser cladding process parameters,and the phase composition,wear,and corrosion properties of this novel coating were investigated.The study of the microstructure and wear properties of the composites shows that the lattice mismatchδ=27.7%（>15%）between the nanoscale（10-200 nm）reinforced particles Zr B2 and the matrix is a incoherent relationship.The microhardness of the composite is around 83 HV,which is an increase of about 43%compared to the AA6111 Al.At room temperature,the results of dry sliding wear tests under different loads show that the wear rate of the composite is in the range of 8×10-4 to 9.5×10-4（mm3/N·m）,which is about 11.3%to36.7%lower than the corresponding Al alloy.The coefficient of friction of the composite fluctuates in the range of approximately 0.25 to 0.3,significantly lower than that of the AA6111 Al alloy under the same conditions（0.26 to 0.44）.By TEM and XPS analysis,the existence of amorphous Al2O3 was confirmed and the first H3BO3 film with a lubricating effect was found to be generated,putting forward the theory of self-lubrication of Zr B2-system aluminum matrix composites.The FeCuMoTiV high-entropy alloy coating was prepared on the surface of the composite.The experimental results show that the optimum laser process parameters for the layer preparation are 2400W laser power,4 mm/s scanning speed,and 40%lap rate.The coating phases consist mainly of Mo-and V-rich FCC phases and Fe-and Ti-rich body-centered cubic ordered B2 phases.Nanoindentation tests showed an average hardness of798.56 HV and a modulus of elasticity of 175.17 GPa for the FCC phase and 184.58 HV and113.08 GPa for the B2 phase.In the electrochemical tests with simulated acid rain solution（H2SO4 at p H=4）,the corrosion potential of the coating was found to be between-0.25053V and-0.33042V,and the corrosion current density was between 1.9565×10-6 A·cm-2 and2.5759×10-6 A·cm-2,with a much lower corrosion tendency than that of the composite material(corrosion potential of the composites was-0.35131V and the corrosion current density is 4.3907×10-6 A·cm-2.In controlled variable tests of dry sliding wear of the coating,it was found that the wear rate of the coating in the load variable ranged from 2.00×10-4 to 3.35×10-4（mm3/N m）,which is about 64.73%to 75%lower than the wear rate of Zr B2/AA6111 composites under the same conditions year-on-year.Analysis of the wear surface products shows that after wear,a"glaze layer"of mixed oxides containing Fe2O3,Mo O3,Cu O,and Ti O2 is formed on the surface,which acts as a good lubricant.The wear mechanism of the coating is a mixture of mainly abrasive wear,supplemented by adhesive wear,oxidative wear,and fatigue wear. |
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