Microstructure And Properties Of Al_xCrCrCu_0.5FeNi High-entropy Alloy Prepared By Mechanical Alloying

High entropy alloy has become a research hotspot in the field of materials as a new concept of alloy design, concentration of alloying elements in the alloy is similar, High entropy alloy has broken the design mode of traditional alloys with one or two kinds of alloy elements as principal elements. Through the alloy design and metallurgy composition design, The high entropy alloy can obtain better performance than the traditional alloys, such as high hardness, high strength, high corrosion resistance, high oxidation resistance and good high temperature stability, magnetic energy and so on.In this paper, the AlxCoCrCu0.5FeNi (x=0,0.5,1.0,1.5) system high entropy alloy was successfully prepared by mechanical alloying and vacuum hot pressing sintering. Alloy elements was added according to the different parameters, enthalpy of mixing, atomic radius difference, crystal structure and the electronegativity difference, to investigate the effect of phase formation in AlCoCrCu0.5FeNi alloy during alloying process. The effects of Al element content on alloying behavior, microstructure, mechanical properties and friction properties were studied. The effect of heat treatment on the structure, microstructure, hardness and compressive properties of high entropy alloys was studied by heat treatment of the alloy at high temperature (1100 ℃,1200℃ and 1300℃).The study found that the influence of the mixing enthalpy, atomic radius difference, crystal structure and the difference of the electric negative on the evolution of the alloy phase is related to the number of the principal components in the alloy. These factors determine the formation process and the phase structure of the alloy with few main elements. But in the alloy with more kinds of alloy element, the impact of these physical parameters convolution metallographic structure is weakened, high entropy of mixing leads to multiple system free energy decreases sharply and promote principal component between the solid solubility is the main driving force for the formation of the high entropy alloy solid solution.With the increase of Al content, After ball milled and sintering, the phase structure of high entropy alloy for FCC phase is the main phase, BCC phase of secondary phase. With the increase of the content of Al, the content of BCC phase and the lattice constant also increased, the plasticity of the alloy decreases, the hardness and strength increase. Al0 and Al0.5 have good plasticity, low strength, the deformation amount reached 30% and 25.6%, while Al1.0 and Al1.5 have low plasticity, good strength, the hardness and compressive strength reached 483HV、1855MPa and 537HV、2083MPa. With the increase of Al content, the fracture mode of the alloy is gradually changed from ductile fracture to brittle fracture. The wear resistance of alloys is proportional to their hardness, Wear and friction coefficient decreased with the increase of Al content, the friction coefficient and wear rate of Al1.5 alloy are the lowest,0.48 and 1.2mg respectively, the wear mechanism of Al0, Al0.5, Al1.0 are adhesive wear and abrasive wear, Abrasive wear for Al1.5, And has oxidative wear in the process of wear abrasion.After heat treatment at high temperature, the phase structure of the alloy change for single phase structure, and the lattice constants of the alloy becomes larger, the lattice strain decreases, the organization becomes more uniform. The disappearance of the rigid BCC phase make the strength and hardness of the alloy lower, but the plastic was improved, the plastic deformation were above 30%. Al0, Al0.5, Al1.0 alloy did not crack in the process of compression, but Al1.5 alloy crack, Its compressive strength is still as high as 2055MPa and 1971MPa after heat treatment at 1100 ℃ and 1200℃.