Study On Magnetic And Electrochemical Corrosion Properties Of FeCoCrNi High Entropy Alloys

FeCoCrNi high entropy alloy is considered to be one of the most stable high entropy alloy.FeCoCrNi-based high entropy alloy is easy to form solid solution with simple structure and has excellent plasticity and toughness.At present,there are few studies on the m echanism of mechanical properties,magnetic properties and chemical properties of FeCoCrNi-based high entropy alloys with the addition and proportion of light elements.Therefore,on the basis of FeCoCrNi series high entropy alloy with good plasticity and workability,the hardness and electrochemical corrosion were measured by X-ray diffraction(XRD),scanning electron microscope(SEM),VSM,hardness and electrochemical corrosion.By adjusting the composition and content of light elements(Ti,Zr),the weigh t loss of FeCoCrNi-based high entropy alloy was made on the basis of ensuring its excellent mechanical properties.The composition and structure factors affecting its magnetic and electrochemical corrosion properties were revealed,and the relationship between them was studied.At the same time,the mechanical and magnetic properties of Mo and lightweight high entropy alloys are compared to improve the magnetic properties of FeCoCrNi series high entropy alloys and expand their application fields.The main r esults are as follows:(1)The face-centered cubic solid solution in FeCoCrNiTi_x alloy is mainly dendritic.The interdendritic interdendrites are composed of many plate-like structures.Ti is dissolved in the face-centered cubic structure,and the Ti content in the interdendritic region is slightly higher than that in the dendritic region.During solidification,the maximum negative mixing enthalpy of Ni and Ti promotes the formation of(Ni,Ti)rich phase.With the further increase of Ti content,the volume fraction of Laves phase increases obviously,the morphology of Laves phase changes from granular to reticular structure,and the content of rich(Cr,Fe)phase further increases.When the content of Ti is 1at.%,the morphology is transformed into only face-centered cubic phase.Dark dendrites and fine microstructures were observed in the microstructure of FeCoCrNi Zr_x alloy,and the matrix of the three alloys was typical lamellar structure of eutectic alloy.With the increase of Zr content,the width of periodic structure becomes thicker,especially near the interface with Laves phase region and Laves-free phase region.In the region with Laves phase,the structure is a mixture of face-centered cubic phase and Laves phase,which nucleate and grow alternately.With the further increase of Zr content,the periodic structure was refined again.The microstructure diagram of FeCoCrNi Mo shows typical dendritic structure.Both dendrites and Interdendritic are face-centered cubic phase,and the dendrites are mainly composed of dark gray structure and a small amount of light gray structure.(2)The change trend of hardness of FeCoCrNi series alloy is the same,the hardness value increases at first and t hen decreases with the increase of Ti or Zr content,and the hardness value is the highest when the content is0.75at.%.The hardness of FeCoCrNi Mo with the same content is higher than that of the other two high entropy alloys.With the increase of the content of Ti and Zr,the density of high entropy alloy decreases,and the density of FeCoCrNiTi _x with the same content is lower than that of FeCoCrNi Zr_x alloy,while the density of FeCoCrNi Mo is the highest.(3)the static hysteresis curves of FeCoCrNiTi _x high entropy alloy synthesized by room temperature hysteresis show paramagnetic behavior.The curves of the three alloys all show hysteresis,and FeCoCrNiTi ₁ has a wider hysteresis area than FeCoCrNiTi _0.5and FeCoCrNiTi_0.75 alloy,while FeCoCrNiTi_0.75 alloy has the smallest hysteresis.When the content of Ti is0.75at.%,the paramagnetism is the most serious.When the content of Ti continues to increase to 1at.%,its paramagnetism is weakened.In the static hysteresis curve of FeCoCrNi Zr _x high-entropy alloy,FeCoCrNi Zr_0.5 and FeCoCrNi Zr_0.75 alloys all exhibit paramagnetic behavior,while FeCoCrNi Zr₁ alloy exhibits typical ferromagnetism,and the coercive force Hc is smaller(1115.1986A/m).The saturation magnetization Mc(8.5625Am²/kg)is relatively large,wh ich is characteristic of soft magnetic properties.In the hysteresis curve of FeCoCrNi Zr _x alloy,only FeCoCrNi Zr_0.5 shows a large hysteresis,FeCoCrNi Zr _0.75 and FeCoCrNi Zr₁alloys have a small hysteresis area,and the hysteresis area of FeCoCrNi Zr_0.75 alloy is basically zero.When the content of Zr is 0.75at.%,the paramagnetism is the most serious.However,when the content of Zr continues to increase to 1at.%,its magnetic properties change from paramagnetism to ferromagnetism.The static hysteresis curve of FeCoCrNi Mo alloy shows ferromagnetism,low coercivity(4681.0678A/m)and high saturation magnetization(1.3638Am²/kg),showing soft magnetic properties.Among the FeCoCrNi high entropy alloys with the same content,FeCoCrNi Zr has the highest saturation magnetization,while FeCoCrNi Mo takes the second place.(4)with the increase of Ti content,the corrosion potential of FeCoCrNiTi_x high entropy alloy increases at first and then decreases.The Nyquist curve of FeCoCrNiTi _x high entropy alloy has diffusion impedance,and the semicircle radius of Nyquist curve of FeCoCrNiTi ₁ is the largest,and the diffusion impedance is also the largest.With the increase of Ti element in the alloy,the diameter of Nyquist semicircular arc decreases at first and then increases.The phase angle of FeCoCrNiTi₁ high entropy alloy is the largest and the polarization resistance R_p is the largest,indicating that the corrosion rate is the slowest and FeCoCrNiTi₁ has better corrosion resistance.With the increase of Zr content,the corrosion potential of FeCoCrNi Zr_x high entropy alloy increased at first and then decreased,while the corrosion current density decreased at first and then increased.There is an obvious passivation zone in all the three alloys,and the activation-passivation transition occurs.The Nyquist diagram of FeCoCrNi Zr_x high entropy alloy is semicircular.It can be seen that with the increase of Zr element in the alloy,the diameter of Nyquist semicircle arc increases at first and then decreases.FeCoCrNi Zr_0.75 has the largest semicircle radius,the largest phase angle and the largest polarization resistance R_p,indicating that it has the slowest corrosion rate and the best corrosion resistance.Compared with the corrosion potential and corrosion current density of FeCoCrNiTi₁and FeCoCrNi Zr₁ high entropy alloy,FeCoCrNi Mo has lower corrosion potential and higher corrosion current density.The semicircle radius of FeCoCrNi Mo Nyquist curve is smaller than that of FeCoCrNiTi₁ and FeCoCrNi Zr₁ high entropy alloys.It can be found that the semicircle radius of FeCoCrNiTi₁ is the largest,while that of FeCoCrNi Mo is the smallest.The phase angle of FeCoCrNi Mo high entropy alloy is the lowest among the three alloys with the same content,and its corrosion resistance is worse than that of FeCoCrNiTi₁ and FeCoCrNi Zr₁ high entropy alloy.It shows that the corrosion resistance of Ti element with the same content is stronger than that of Zr element and Mo element.These studies not only provide a profound understanding of the effect of alloying on the microstructure evolution and mechanical properties of high entropy alloys,but also provide valuable information for the design of super high entropy alloys in microelectronic devices,lightweight hig h entropy alloys and advanced coating industry.Figure[47]table[9]reference[105]...