First Principles Study Of PtPdRhIr And TiZrHfNb High Entropy Alloys

Since the concept of multi-component high-entropy alloys was proposed by Professor Ye Junwei,high-entropy alloys have attracted more and more attention due to their unique design concepts and significant high-entropy effects.The significant difference between high-entropy alloys and traditional alloys lies in the number of constituent elements.Traditional alloys are usually composed of only one or two main elements,while high-entropy alloys are composed of more kinds of main elements.High-entropy alloys have been proven to have some unusual mechanical and physical properties,such as having the advantages of high strength and high ductility at the same time,which are difficult to achieve in traditional intermetallic compounds.At present,research on high-entropy alloys mainly focuses on the formation theory,design and preparation,performance,and strengthening mechanism of high-entropy alloys.Although people have done a lot of experimental and theoretical research on the structure-property relationship,they are concerned with the high-entropy effect caused by the There is still only a vague understanding of the mechanical properties,which cannot be explained from the perspective of electrons and atoms.The first-principles calculations of high-entropy alloys can theoretically reveal the reasons for the changes in the mechanical properties of high-entropy alloys.In this paper,a special quasi-random structure model is used to establish the structure of the alloy,this paper studies the structure and elastic properties of PtPdRhIr high-entropy alloy with different pressure and different Ir content and Ti Zr Hf Nb high-entropy alloy under different pressure,and studies the thermodynamic properties of high-entropy alloy at finite temperature with thermodynamic Debye model,which provides theoretical guidance for the design of high-entropy alloy.The main contents of this article is as follows:（1）The stability criterion of PtPdRhIr high entropy alloy is analyzed.The SQS special quasi disorder model of PtPdRhIr high entropy alloy is generated by using mcsqs algorithm code in ATAT software.The elastic properties of PtPdRhIr high entropy alloy under different pressures are explored,and its yield strength is predicted.The stability and physical essence are explained from the Perspective of electronic structure.It is found that the anti deformation ability can be improved by increasing the pressure appropriately,The ductility and anisotropy of ptpdrhir high entropy alloy increase with the increase of pressure.（2）the effects of Ir content on the stability,elasticity and thermodynamics of PtPdRhIr high entropy alloy were investigated and the yield strength was predicted.The yield strength of Pt₃₃Pd₃₃Rh₃₃Ir₉is the highest.With the increase of Ir content,the elastic modulus and microhardness will increase,but the entropy changes little under different Ir content,which mainly comes from the contribution of vibration entropy and the heat capacity mainly comes from the contribution of lattice vibration.Its stability and physical nature are explained from the point of view of electronic structure.（3）the XRD and simulated XRD patterns of Ti Zr Hf Nb high entropy alloy prepared by arc melting are consistent under different pressures.It is proved that Ti Zr Hf Nb high entropy alloy is BCC structure.The structure,elastic properties and thermodynamic properties are calculated by VASP,and it is found that it has been unstable at 10GPa,which is consistent with that observed in the experiment.The deformation resistance of Ti Zr Hf Nb high entropy alloy increases with the increase of pressure,and the entropy of Ti Zr Hf Nb high entropy alloy increase with the increase of temperature.Through the experiment to compare the thermal expansion coefficient,it is found that the experimental results are consistent with the calculated results.The phenomenon of instability in 10GPa is also found from the point of view of electronic structure.