Refractory High-entropy Alloys Design Based On Empirical Electron Theory Of Solids And Molecules

High entropy alloys?HEAs?are composed of five or more elements which have equal mole or near equal mole ratios.To date,high-entropy alloys'research seems to emphasize alloys based on the late transition metals such as Fe,Ni,Co and Cu.To the authors'knowledge,there have been no systematic efforts to explore HEAs based primarily on refractory element constituents.On the other hand,since empirical electron theory of solid and molecules?referred to as EET?has been founded,the scholars has studied relationship between valence electron structure?referred to as the VES?of a variety of materials and static properties quantitative,but the study about HEAs'performance was rare.In view of this,this paper proposed using EET theory to guide the design of high entropy alloys.The three series of Zr_?l?Ti_?m?Hf_?n?V_?x?Nb_?y?,Zr_?l?Ti_?m?Hf_?n?Nb_?x?Mo_?y?,Zr_?l?Ti_?m?Hf_?n?Nb_?x?Ta_?y?,of HEAs were choosen to be the research object.High entropy alloys of different compositions of valence electron structure parameters were calculated,and using the valence electron structure parameters to predict alloy performance,choosing the alloys with special performance for preparation with electricity arc furnace and its mechanical properties and microstructure were analyzed.Research shows that:the refractory high entropy alloys had formed a single body centered cubic crystal structure or face-centered cubic structure.A series alloy of Zr_?l?Ti_?m?Hf_?n?Nb_?x?Mo_?y?have stronger high temperature softening resistance,and the high temperature compression strength of ZrTiHfNb₂Mo₂ at 700?can be 1155 MPa,the dynamic compression strength at room temperature reaches more than 3800 MPa.In dynamic compression experiments,alloys had no obvious reinforcement effect of strain rate,alloys are experienced in the process of compression elastic deformation,plastic deformation and failure stage.ZrTiHfVNb₂ alloy shows good mechanical properties,static compress yield strength is 1114 MPa,plastic strain is more than 50%,the static tensile strength is 880 MPa and the tensile strain is 11%.The hardness of alloys have a close relationship with alloys'elements and elements'content,the more high melting point element,the higher hardness is and ZrTiHfNb₂Mo₂ alloy's hardness is 540 HV.The amount of alloy's common electronic named n_A which determines the strength of high entropy alloys and high temperature resistant ability to soften.The value of the sum of covalent bond?n_C has a reverse trend of the plastic strain,and it with the possible atomic state group number in the phase named N codetermines the plastic of alloys.