First Principles Study The Influence Of Transition Metal Elements On The Mechanical And Thermodynamic Properties Of Palladium-based Alloys

Platinum-group-metal(PGMs)superalloys can be used as a good alternative to nickel-base superalloys because PGMs have the same face centered cubic(fcc)structure as Ni-Base superalloys,the melting point of PGMs is higher than that of NiBases,and they are stability.However,the current research mainly focuses on Pt,Ir and Rh-Based superalloys,but these three kinds of precious metals are expensive,have higher density,and have less resources.The price and density of palladium are relatively low.At present,there is insufficient attention to Pd-Based alloys.The main reason is that the mechanical properties of pure Pd is poor.In this paper,we study that the transition metals(TM: Al,Si,Sc,Ti,V,Cr,Mn,Fe,Cu,Zn,Y,Zr,Nb,Mo,Tc,Hf,Ta,W,R,Os,Pt)and palladium form solid solution strengthening to improve the mechanical properties of Pd-Basedsuperalloys.The crystal structure,mechanical properties and thermal properties of Pd-TM binary compounds and Pd31 TM superaloys were calculated by first-principles calculations.Comparative analysis was carried out to complete the screening process of alloying elements.In this paper,t he method can shorten the research and development cycle,reduce costs,and save precious metal materials.To further enrich the basic theoretical research of platinum-group-metals superaloys and promote the development and application of platinum-group-metals superaloys.The main research results obtained in this paper are as follows:The cohesive energy and formation(mixing energy)enthalpy of Pd-TM(TM=Ti,Zr,Hf),Pdx Vy and Pd31TM(TM=Ti,Zr,Hf)are negative,indicating that they are thermodynamic stable.The elastic constants,elastic modulus of superalloys are mechanically stable by the mechanical stability cnditions.The result of C11,B,G of Pd Ti is biggest,the values are 204.8 GPa,36.9 GPa ? 103.2 GPa.The anisotropy of superalloys is related to the m icro cracks.By analyzing the DOS,differential charge density of these materials to study their physical nature,it is found that these compounds have metallic properties.By studying the thermodynamic and mechanical properties of Pd-TM(TM=Ti,Zr,Hf)and Pd31TM(TM=Ti,Zr,Hf),Pd31TM(TM=Ti,Zr,Hf)improve the higher mechanical properties of Pd alloys than Pd-TM(TM=Ti,Zr,Hf).We researched the thermodynamic stable of Pdx Vy compounds,found enthalpy of formation of ?-Pd2 V is the lowest,-0.34 e V/atom,which ?-Pd2 V is the most stable among Pdx Vy compounds.The modulus of Pdx Vy compounds are calculated,the value C11 ? C33 of ?-Pd3 V are the largest,508.4.7 GPa and 624.1 GPa respectively.Based on the above work,the following 21 alloys elements in Pd-Based superalloys are determined: Al,Si,Sc,Ti,V,Cr,Mn,Fe,Cu,Zn,Y,Zr,Nb,Mo,Tc,Hf,Ta,W,R,Os and Pt.The addition of transition alloy elements makes the mechanical properties o f the Pd-Based improved.The mechanical anisotropy of them is also studied.It is found that they are anisotropic,and the order of anisotropy is as follows: Pd31Pt> Pd31Al(Pd31Cu)> Pd31Mn> Pd31Si> Pd31Zn(Pd31Y)> Pd31V> Pd31Sc(Pd31Cr)> Pd31Ta>Pd31Nb(Pd31Mn,Pd31W)> Pd31Tc(Pd31Re)> Pd31Os> Pd31Ti> Pd31Hf> Pd31Zr> Pd31 Fe ?...