Effect Of Alloying Agent On Microstructure And Properties Of High-entropy Alloy

Principal elements of high-entropy alloys are only just emerging in recent years, which is a new type of material science. High-entropy alloys based on equimolar or nearly equimolar ratio five or more than five key elements, taking melting, sintering or other means to get a combination of the metallic material. The increase of the key elements lead to produce high-entropy effect, crystal structure tend to form a simple body-centered or simple face-centered structure, intergranular compounds also may be accompanied by the generation, even in the cast it will be precipitated nanocrystals. This phenomenon is playing a solid solution strengthening, precipitation strengthening and dispersion strengthening effect, which making the performance of high-entropy alloys have greater advantages compared to conventional alloys.The high-entropy alloys Alo.5CoCrCuFeNiBx, Al0.5CoCrCuFeNiSix and Co1.5CrFeNi1.5Ti0.5AlxMoy were designed on the basis of composition design criterions. Alloy ingots were prepared by vacuum arc furnace. The crystalline structure of alloy was characterized using X-ray diffraction (XRD). The microstructure and micro area composition of alloy was studied by SEM equipped with EDS. The microstructure hardness of alloys was tested on the universal testing machine.High-entropy alloys of three series of alloys were all single phase solid solution, and also were FCC, BCC and FCC+BCC solid-solution structure. This could be attributed to that the effect of high mixing entropy did facilitate the formation of simple solid solutions. High-entropy alloys of Al0.5CoCrCuFeNiBx exhibited excellent hardness properties. With the increase of B content, the hardness of these alloys increased. The hardness of these alloys reached 607 HV when B reached x=1.0. And the results showed that the precipitation of Cr2B, (Cr, Fe) B could not be restrained in the alloys. And the lattice parameters of Al0.5CoCrCuFeNiBx high-entropy alloys changed little. High-entropy alloys of Al0.5CoCrCuFeNiSix exhibited excellent hardness properties. With the increase of Si content, the hardness of these alloys increased. The hardness of these alloys reached 1011 HV when Si reached x=1.0. And the results showed that the precipitation of CrSi2, Fe2Si could not be restrained in the alloys when Si reached x=0.4 or x=1.0. And the lattice parameters of Al0.5CoCrCuFeNiSix high-entropy alloys decreased when Si was added. High-entropy alloys of Co1.5CrFeNi1.5Ti0.5AlxMoy formed simple solid solution. The hardness of these alloys changed little with the addition of Al and Mo. The lattice parameters of Co1.5CrFeNi1.5Ti0.5AlxMoy high-entropy alloys did not have significant difference when Al and Mo were added.Al0.5CoCrCuFeNiBx, Al0.5CoCrCuFeNiSix and Co1.5CrFeNi1.5Ti0.5AlxMoy high-entropy alloys are superior to the traditional alloy in mechanical properties, which can be greater to adapt to the needs of industrial production, its development and application prospects.