Research On Preparation,Microstructure And Properties Of FeCrNiMnM(M=Mo,Al) High Entropy Alloys

Unlike traditional alloys,high entropy alloys?HEA?are new type of material with stable solid solution composed of more than five main components,which has high strength,high toughness,wear resistance,corrosion resistance.Due to its excellent properties,such as heat resistance and oxidation resistance,it has attracted widespread attention.In this study,vacuum arc melting and laser surface remelting modification were used to synthesize the FeCrNiMnMo_x and FeCrNiMnAl_y HEAs,and studied the potential impact of Mo and Al on the material structure,mechanical properties and electrochemical corrosion properties.The research in this article shows:FeCrNiMnMo_x?0,0.1,0.3,0.5,0.8,1? HEAs changed from FCC to FCC phase and?phase.With the increase of Mo content,the microhardness of the alloys increases,and the yield strength increases first and then decreases.The increased volume fraction of?phase plays an important role in improving the compressive strength of the alloy,and compression performance is significantly affected by solid solution strengthening and second phase strengthening.Among them,the microhardness of FeCrNiMnMo₁ alloy is 3.6 times that of FeCrNiMn alloy,and the yield strength of FeCrNiMnMo_0.5 alloy is the largest,which is 896.2 MPa.The electrical resistivity of FeCrNiMnMo_0.3 alloy is the maximum of 144??·cm.In the 3.5%NaCl solution,FeCrNiMnMo_0.1 alloy has the best corrosion resistance,and the pitting corrosion resistance of the alloy increases with the increase of Mo content.In 0.5M H₂SO₄solution,FeCrNiMnMo_0.1alloy has the best corrosion resistance,and the passivation film formed is mainly composed of Cr and Mo oxides.Besides,the protective ability of the passivation film depends largely on the composition of the film,of which FeCrNiMnMo_0.1alloy has large amount of Cr oxide in the passivation film and good corrosion resistance.The FeCrNiMnAl_y?0,0.3,0.5,0.8,1?HEAs transforms from FCC phase to BCC and B2 phases.With the increase of Al content,the microhardness of the alloys increases,and the yield strength increases first and then decreases.This is because it is mainly affected by solid solution strengthening and precipitation strengthening.Among them,the microhardness of FeCrNiMnAl₁alloy is 2.5 times that of FeCrNiMn alloy,and FeCrNiMnAl_0.8alloy has the largest yield strength,which is 1269.6 MPa.The electrical resistivity of FeCrNiMnAl_0.5alloy is the minimum of 85??·cm.In 3.5%NaCl solution,with the content of Al increases,the corrosion resistance of the alloy decreases.In 0.5M H₂SO₄solution,with the Al content increases,the corrosion resistance of the alloy decreases.In addition,compared to FeCrNiMnAl_0.5alloy,the corrosion resistance of the passivation film of the FeCrNiMnAl₁ alloy decreases with increasing thickness,which is caused by the decrease in density of the passivation film.The FeCrNiMnMo_x?x=0,0.5,1?and FeCrNiMnAl_y?y=0.3,0.5,1? HEAs remelted layer have the same composition as the as-cast high entropy alloy,and it is dominated by dendrite structure.In the 3.5%NaCl solution,with the content of Mo increases,which improves the corrosion resistance of the remelted layer of FeCrNiMnMo_x HEAs.This is because the addition of Mo promotes the formation of Cr³⁺and improves the corrosion resistance of the protective film of the alloys remelting layer.In 3.5%NaCl solution,with the increase of Al content,the corrosion current density and corrosion rate of the remelted layer of FeCrNiMnAl_y HEAs decrease first and then increase.Among them,the corrosion current density and corrosion rate of the remelted layer of FeCrNiMnAl_0.3alloy lowest.In addition,compared with FeCrNiMn alloy,the increase of Al³⁺content and the decrease of Cr³⁺content in the FeCrNiMnAl₁ alloy remelting layer protective film indicate that the density and protection of the protective film decrease.