Microstructure And Room Temperature Mechanical Properties Of Fe-Cr-Ni-Al-Ti High Entropy Alloys

Material is the material basis for human survival,and the development of human history is closely related to the development of materials,especially the development of metal materials,which is the label of the times and civilization.High-entropy alloys have been developed in recent years.They are different from traditional alloys in that one or two alloying elements are used as the main elements and other elements are supplemented.High-entropy alloys are composed of many elements,each of which is the principal component.They are simple solid solutions formed by molar ratio or approximate equal molar ratio.They have excellent properties such as high strength,high hardness,high wear resistance and corrosion resistance.Fe-Cr-Ni-Al-Ti high-entropy alloys were prepared by vacuum arc melting.The effects of Cr and Ni alloying elements on the microstructure and properties of high-entropy alloys were studied.By means of XRD,SEM and EDS,the phase and morphology of the alloy were studied.It was found that with the decrease of Cr and the increase of Ni,the high-entropy alloy transformed from BCC+FCC solid solution to FCC single-phase solid solution,and the crystal structure and morphology changed obviously.The mechanical properties of the alloys were analyzed by room temperature compression test and micro Vickers hardness.The first three types of the alloys were characterized by BCC+FCC biphasic structure,which exhibited higher strength and hardness.The latter two types were FCC solid solution,which exhibited higher ductility but lower strength.In traditional alloys,as-cast metals are usually treated by heat treatment,which can eliminate internal stress and segregation,and improve the properties of metals.In this paper,the heat treatment of as-cast high-entropy alloys with five components was carried out.The effect of heat treatment on the microstructure of high-entropy alloy was studied by XRD,SEM and EDS.The mechanical properties of high-entropy alloy were characterized by room temperature compression test and micro hardness test.The results show that heat treatment has a significant effect on high-entropy alloy.New phases appear in the first three types of alloys during high temperature heat treatment,and the morphology of the microstructures varies greatly,as well as the compressive properties and micro hardness at room temperature.For the latter two groups,the change of phase is not obvious.From the XRD spectrum,it is only the change of peak strength,and the change of micro-structure morphology is not obvious.However,the mechanical properties of samples have changed dramatically.The yield strength of Fe40Cr25Ni25Al5Ti5 has increased from 180 MPa as-cast to 460 MPa(800 °C /12h),the hardness has also increased from 210 HV to 380 HV(1000 °C /12h),and the yield strength of Fe40Cr20Ni30Al5Ti5 alloy has also increased from 620 MPa as-cast to 850 MPa.The maximum temperature of 620 HV is reached at 1000 °C /12 h,which is 47.6% higher than that of as-cast.