Research On Composition,Microstructure And Tribology Properties Of Fe-Cr-Ni-Mn System High Entropy Alloys

The high entropy alloy is an innovative alloy material which consists of five or more principal elements.Due to its unique four core effects of high mixing entropy,hysteresis atomic diffusion,cocktail effect and X,this new alloy has excellent comprehensive properties.In this paper,based on Fe Cr Ni Mn high entropy alloy,the Al atom and the interstitial C atom are used for microalloying.X-ray diffraction（XRD）,scanning electron microscope with energy spectrometer（SEM-EDS）,Vickers hardness tester,universal material testing machine,multi-functional friction machine and other experimental instruments are used to study the microstructure,mechanical and tribological properties of as-cast and heat-treated high-entropy alloys after aging.The effects of Al,Fe and C on the properties of alloys were studied.The results are as follows:In FeCrNiMnAl_x（x=0,0.3,0.5,0.8,1.0）high entropy alloys,the microstructure of Fe Cr Ni Mn alloy is dominated by FCC phase,and the dendrite microstructure of FCC+BCC+B2 phase is found in Fe Cr Ni Mn Al0.3 alloy.With the Al content increasing to0.5,The interdendrite structure of BCC+B2 appeared.With the increase of Al content,the microhardness and yield stress of Fe Cr Ni Mn Al_x high entropy alloy are obviously improved by solution strengthening and second phase strengthening.The microhardness of Fe Cr Ni Mn Al1.0 alloy is 483 HV,1.5 times higher than that of Fe Cr Ni Mn alloy.The yield strength of Fe Cr Ni Mn Al_x alloy increased from 297 MPa to 1269 MPa.The wear resistance of Fe Cr Ni Mn Al_x high entropy alloy increases with the increase of Al content,while the average wear volume loss of Al0.8 alloy is 0.416 mm3,and the average roughness of the wear marks is the smallest.The wear mechanism of FeCrNiMnAl_x high entropy alloy is mainly abrasive wear,showing the best wear resistance.In Fe_yNiMnCr_0.5Al_0.5（y=1.0,1.5,2.0）high entropy alloy,there are always a large number of FCC phase and a small amount of BCC.With the increase of Fe content in the alloy,the proportion of BCC phase in the alloy decreases,and the microhardness and compressive strength of the alloy gradually decrease.The maximum hardness of Fe_1.0 high entropy alloy is 286 HV and the compressive strength is 2633 MPa.When Fe content is increased to y=2.0,the alloy exhibits excellent plasticity in mechanical properties.After heat treatment,the microhardness of Fe_2.0 alloy reaches 244 HV,and the average wear rate is 1.256×10^-3 mm³/（N·m）.It is a low-cost high-entropy alloy with excellent mechanical properties and poor tribological properties.The addition of C can improve the properties of the alloy by solution strengthening and carbide precipitation strengthening.In Fe₂Ni Mn Cr_0.5Al_0.5C_z（z=0,0.05,0.10,0.15）high entropy alloy,the microstructure is always FCC matrix phase+a little BCC phase.With the increase of C content,the BCC phase in the microstructure of the alloy is enhanced.After heat treatment,al-Ni phase appears at（200）and（211）.With the increase of carbon content,the strength and hardness of the alloy gradually increase,and the compression test shows that the alloy shape decreases.After 600℃×5h heat treatment and air cooling,when C content is z=0.15,the average grain size of the alloy is refined,carbide precipitates at the grain boundary of the matrix and within the grain,resulting in reduced alloy shape and improved hardness.At this time,the microhardness of the alloy reaches 613 HV,and the mechanical properties of the alloy are improved compared with the as-cast state.At this time,C_0.15 alloy shows excellent tribological properties with an average wear rate of 0.050×10^-3mm³/（N·m）,and the wear mechanism is mainly abrasive wear.