Study On The Composition Design And Performance And Mechanism Of High Entropy Alloys With High Saturated Magnetization

Compared with traditional alloys,high-entropy alloys have attracted more and more attention due to their unique phase structure and comprehensive properties.A large number of studies have shown that Fe Co Ni-based high-entropy alloys can have good mechanical and magnetic properties at the same time,so they can be used in the development of magnetic materials in the future.However,in the magnetic high-entropy alloy systems that have been developed so far,the saturation magnetic induction(B_S)is generally low,so there is still room for further improvement.In the literature on such high entropy alloys,most of them are mainly concentrated on high-entropy alloys with equal atomic ratios of Fe,Co,and Ni,and most of the researches only explore from an experimental point of view,and there is still a lack of theory on the relevant magnetic mechanism.the study.Therefore,this article firstly uses the first-principles method to discuss the influence of common non-ferromagnetic elements Cr and Mn on the magnetic properties of Fe Co Ni Si_0.2M_0.2high entropy alloys.Then,on this basis,breaking through the limitations of Fe Co Ni and other atomic ratio design ideas,designed a series of Fe₄₀Co₄₀Ni₁₀M₁₀(M=Al,Cr,Cu,Mn,Si)high entropy alloys,and explored the magnetics,mechanics,and Corrosion resistance.The results show that different additive elements have significant effects on the phase structure and magnetic properties of the high entropy alloys.Therefore,the mechanism of the magnetic difference of the above-mentioned materials is explored from a microscopic point of view using a combination of first principles and molecular dynamics simulation.The above research can provide a certain reference and reference for the development of high-performance magnetic high-entropy alloys.The main research results of this paper are as follows:(1)The unit cell model produced by the special quasi-disordered structure(SQS)can better simulate the solid solution structure of the high-entropy alloy.The XRD pattern is in good agreement with the experiment,and magnetic properties obtained by first-principle calculations is also consistent with the experiment.Although both Cr and Mn are antiferromagnetic elements,the magnetic difference caused by the addition to Fe Co Ni-based high-entropy alloys is very large.It is found that the addition of Mn leads to significant enhancement in B_Sand T_Cof the Fe Co Ni Si_0.2M_0.2HEA compared to Cr,which is caused by the changes of electron-spin that lead to ferromagnetism of Mn,and such phenomenon may have close correlation with the ferromagnetic coupling between Mn and Fe Co Ni matrix.(2)Through structural analysis,it can be seen that Fe₄₀Co₄₀Ni₁₀M₁₀(M=Al,Mn,Si)has a single BCC structure,while Fe₄₀Co₄₀Ni₁₀M₁₀(M=Cr,Cu)has a single FCC structure,which means that the added elements play a role in the phase formation of the high-entropy alloy.Important role.At the same time,different non-magnetic elements have a great influence on the magnetic,mechanical and corrosion resistance of high-entropy alloys.Among them,the elements(Al,Mn and Si)that contribute to the formation of the BCC phase can increase the strength and Bs value of the high-entropy alloy,and the elements(Cr,Cu)that contribute to the formation of the FCC phase can increase the high-entropy of the system.The plasticity of the alloy,but will significantly reduce Bs.In addition,Al and Cr elements can effectively reduce coercivity and improve corrosion resistance.Among the above magnetic high-entropy alloys,the B_Svalue of Fe₄₀Co₄₀Ni₁₀M₁₀(M=Al,Mn,Si)high-entropy alloys with BCC structure can reach?190 emu/g,which is significantly higher than the current widely researched and developed magnetic high-entropy alloy system,and Fe₄₀Co₄₀Ni₁₀M₁₀has the best overall performance in terms of magnetic performance,mechanical properties and corrosion resistance.(3)By comparing the formation energy of the BCC and FCC phase structure of each alloy composition,it can be determined that alloys containing Cr and Cu components tend to form FCC phases,while alloys containing Al,Mn and Si components more inclined to generate the BCC structure,which is consistent with the experimental results;the main reason why the B_Sof the BCC structure is significantly higher than the FCC structure is that the average magnetic moment of the ferromagnetic element in the BCC structure is significantly higher than that of the FCC structure.(4)Analyzing the magnetic difference between the two from the perspective of electronic properties,it can be found that the number of spin-up electrons in the BCC structure is significantly higher than that in the FCC structure,while the spin-down electron distribution is exactly the opposite.By calculating the correlation function of the two structures,it can be found that compared with the BCC structure,the FCC structure is more inclined to generate Fe-M,Co-M and Ni-M atom pairs,and the magnetic moments in the two structures the distribution difference has a lot to do with this short-range chemical sequence.