Study On Microstructure And Properties Of Al-Cr-Fe-Ni High Entropy Alloys Based On Phase Proportion Design

High entropy alloy is a novel alloy which breaks the traditional alloy design concept in recent years.It has multiple principal elements with equal molar ratio or near equal molar ratio.Due to the high entropy effect,multi-principal high entropy alloys tend to form solid solutions rather than a lot of complex intermetallic compounds.Therefore,the high entropy alloy has many outstanding properties,such as high strength,high hardness,good wear resistance,excellent corrosion resistance and so on.The phase composition of the high entropy alloy can be adjusted by changing the composition and controlling valence electron concentration,but how to control the phase ratio in the alloy also needs to be further studied.AlCrFe₂Ni₂ eutectic high entropy alloy consists of FCC phase and BCC phase,in which the composition of FCC phase is Al_9.4Cr_19.7Fe_41.4Ni_29.5 and the composition of BCC phase is Al21.7Cr15.8Fe28.6Ni33.9.Therefore,?Al21.7Cr15.8Fe28.6Ni33.9?x?Al9.4Cr19.7Fe41.4Ni29.5?100-x high entropy alloys were designed to control the phase ratio of the alloys in this paper.The microstructure and properties of high entropy alloy were studied by scanning electron microscopy?SEM?,X-ray diffraction?XRD?,Vickers hardness tester and electronic universal testing machine.In addition,the physicochemical parameters of high entropy alloy were calculated and discussed.The results show that(Al_21.7Cr_15.8Fe_28.6Ni_33.9)_x(Al_9.4Cr_19.7Fe_41.4Ni_29.5)_100-x high entropy alloys are composed of FCC phase,disordered BCC phase?A2?and ordered BCC phase?B2?.When x value increases from 10%to 90%,the BCC phase volume fraction of alloys increases from 5.32%to 98.81%.Although there is a certain error between the BCC phase volume fraction of alloys and the designed value,the variation trend of BCC phase volume fraction is still consistent with the design.The valence electron concentration is an important parameter affecting the volume fraction of BCC phase in alloys.When the valence electron concentration of the alloy decreases,the alloy system tends to form BCC phase.With the increase of x value,the hardness of high entropy alloys increases from 186 HV to 431 HV,and the yield strength increases from 310 MPa to 1268 MPa.At the same time,the plasticity of the alloy decreases,but the overall plasticity of the alloy is excellent,and the minimum compressive strain is 33.85%.The friction coefficient and wear depth of(Al_21.7Cr_15.8Fe_28.6Ni_33.9)_x(Al_9.4Cr_19.7Fe_41.4Ni_29.5)_100-x high entropy alloys decrease with the increase of x value,so the wear resistance of the alloy system is gradually improved.As the volume fraction of BCC phase increases,the wear surface roughness of the alloy decreases and the wear surface becomes smoother.With the x value is 90%,the wear mechanism of the alloy is abrasive wear.When the volume fraction of BCC phase increases,the deformation resistance of the alloy is enhanced in(Al_21.7Cr_15.8Fe_28.6Ni_33.9)_x(Al_9.4Cr_19.7Fe_41.4Ni_29.5)_100-x high entropy alloys.Therefore,the hardness,strength and wear resistance of the alloy are improved.The volume fraction of BCC phase is the main factor having affection on the strength and plasticity of the alloy.