The Composition Design And First Principles Calculation Of Monbta-Based Refractory High Entropy Alloys

In this paper,in order to obtain refractory high-entropy alloys with single phase BCC structure which present excellent comprehensive properties,MoNbTaCrV,MoNbTaZrV,MoNbTaTiV and MoNbTaTiZr four refractory high-entropy alloys were designed and prepared by using Mo,Nb and Ta elements as the matrix to ensure the molar amount of the whole body was 60%.Based on these alloys,Cr,V,Ti and Zr elements were added.The microstructures,chemical compositions,mechanical properties at room temperature,conductivity and electrochemical corrosion properties of alloys were studied by X-ray diffractometer,metallographic microscope,scanning electron microscope,universal testing machine and electrochemical workstation.And then,based on the MoNbTaTiV alloy with excellent comprehensive performance,the contents of Ti and V elements were changed.?MoNbTa?₆Ti_xV_yrefractory high-alloys were designed,prepared and homogenized,and the microstructures and properties were investigated.Finally,the structures,energy,stability and conductivity of?TaNb?_0.67?HfZrTi?_0.33,MoNbTaCrV,MoNbTaTiV and MoNbTaTiZr alloys were studied by first principles calculation under different hydrostatic pressure.The results show that the microstructures of as-cast MoNbTaCrV,MoNbTaZrV,MoNbTaTiV and MoNbTaTiZr alloys were composed of dendritic structures.MoNbTaCrV and MoNbTaTiV alloys all form a single phase BCC solid solution.MoNbTaTiV alloy shows obvious plastic characteristics,a compression strength of 1490MPa,the plastic deformation rate of 9.64%,and it has an obvious passivation zone appearing in 3.5%Na Cl solution.MoNbTaTiV alloy shows the best comprehensive performance in these four as-cast alloys.All?MoNbTa?₆Ti_xV_yalloys form solid solutions with single phase disordered BCC structure,and their metallographic structures are typical dendrite structures.These?MoNbTa?₆Ti_xV_yalloys show compression strengths of 1027?1500 MPa,plastic deformation rates between6.69?12.39%.The ordered phase is formed after homogenization treatment.Mechanical properties are improved with the increasing of Ti element content for the homogenization treated alloys.MoNbTaTiV and?MoNbTa?₆Ti_2.5V_1.5alloys have the most outstanding comprehensive performances.As the hydrostatic pressure increases,the lattice constants and cell volumes of?TaNb?_0.67?HfZrTi?_0.33,MoNbTaCrV,MoNbTaTiV and MoNbTaTiZr alloys decreases,while the energies and the elastic constants increases.The decrease rate of density of state?DOS?at Fermi level for?TaNb?_0.67?HfZrTi?_0.33changes at 160 GPa,which is the main reason for the sudden change of alloy resistivity.When the volume compression ratio of MoNbTaCrV and MoNbTaTiV alloy is 0.80 and 0.59,respectively,there is a change in the decreasing rate of DOS,which indicated that the alloy might have a sudden drop in resistivity under the corresponding high hydrostatic pressure.