First-principles Calculation Of Alloying Element Doping On The Stability And Performance Of ?'-Pt₃Al Phase

Ni-base superalloys are currently the most widely used high-temperature materials in aerospace field.With the development of defense-related science and technology,a new generation of superalloys that could operate at higher temperature is desired.However,the application of Ni-base superalloys is hindered due to the low melting-point of nickel.Recently,researchers have discovered an analogous microstructures of ?' phase in the Pt-Al base alloys,which make Pt-based superalloys becomes a candidate for a new generation of superalloys.As a critical strengthening phase,the structural stability and elastic properties of ?' phase directly determine the overall mechanical properties of Pt-base superalloys.However,it is often blinding to select the alloying elements to stabilize ?' phase by 'trial and error methods' in experimental studies,and it is difficult to characterize the properties of y' phase in experiments.Therefore,in order to guide the design and development of Pt-base superalloys strengthened by ?' phase,it is important to theoretically study the effects of alloying elements on the phase stability and elastic properties of ?' phase.In order to study the performance advantages of the new Pt-based superalloys,the performance characteristics of ?'-Pt3Al and ?'-Ni3Al such as elastic properties,electronic structure and point defect structure were first analyzed and compared.The calculation results of the formation enthalpy and binding energy show that the stability of ?'-Pt3Al was better than that of?'-Ni3Al.The calculation results of elastic properties showed that ?'-Pt3Al phase possesses better elastic deformation resistance than ?-Ni3A? phase.The calculation results of ideal tensile strength showed that the ideal tensile strength of ?'-Pt3Al in the[110]and[111]directions was significantly larger than that of ?'-Ni3Al.The calculation results of the band structure and density of states showed that both ?'-Pt3Al and ?'-Ni3Al phases exhibit metal characteristics,and the Pt-Pt,Pt-Al(Ni-Al)bonds were formed.Further population analysis showed that ?'-Pt3Al phase exhibits better covalent properties than the ?'-Ni3Al phase.In this paper,the single point defect structure of?'-Pt3Al and ?'-Ni3Al phases were also studied.By calculating the equilibrium solubility of point defects,it found that the vacancy concentration of ?'-Pt3Al is lower than ?'-Ni3Al at high temperature,indicating that the high temperature creep resistance of ?'-Pt3Al was better than that of ?'-Ni3Al.In this paper,the effects of the doping of alloying elements M(M=Sc,Ti,V,Cr,Mn,Fe,Co,Ni,Y,Zr,Nb,Mo,Tc,Ru,Rh,Pd,Hf,Ta,W,Re,Os,Ir)on the ?'-Pt3Al phase was mainly calculated.The calculation of the site preference energy(?Esite)indicated that the alloying elements including Ir,Fe,Ni,Pd,Rh tend to occupy the Pt position,while the V,Ta,Hf,Y,Zr,Nb,W,Re,Mo,Sc,Ti,Cr,Tc,Mn,Ru,Os,Co tend to occupy the Al site.The calculation results of stable formation energy(?Estab)showed that alloying elements V,Ta,Hf,Y,Zr,Nb,W,Re,Mo,Sc,Ti,Cr,Tc,Mn,Co can effectively stabilize ?'-Pt3Al phase.The analysis of the B/G value of the ternary compound Pt24Al7M indicated that the doping of the alloying elements M(M=Sc,Ti,V,Cr,Mn,Co,Y,Zr,Nb,Mo,Tc,Hf,Ta,W,Re)didn't change the intrinsic toughness property of the?'-Pt3Al phase.The analysis results of elastic anisotropy showed that the influence of the doping of 4d and 5d transition metal elements on the elastic anisotropy was the same of the effect on the volume change of ?'-Pt3Al phase,that is both of them gradually decreased as the atomic number increased.The analysis results of elastic properties and thermodynamic properties showed that the effects of different alloying elements on the properties of ?'-Pt3Al phase were different.3d transition metal elements(Sc,Ti,V,Cr,Mn,Co)hadn't regular effects on the performance of?'-Pt3Al phase,while 4d(Y,Zr,Nb,Mo,Tc)and 5d(Hf,Ta,W,Re)transition metal elements had regular effects on the performance of ?'-Pt3Al phase.With the increasing of atomic number,the Mo and Ta elements were used as the demarcation points,and the elastic modulus,Debye temperature and hardness of the 4d and 5d transition metal elements increased first then decreased.The analysis of the electronic structure show that the Pt-Pt metal bond,and the Pt-Al,Pt-M covalent bonds were mainly formed in the ternary compound Pt24Al7M.And the influence of the doping of 4d and 5d transition metal elements on the structural stability and covalent properties was consistent with the effects on the elastic modulus,Debye temperature and hardness.The effect of alloying element doping on the stability and properties of ?'-Pt3Al phase by first-principles method was the innovation of this paper.The structure and mechanical properties of ?'-Pt3Al were studied,and the microscopic mechanism of alloying element ?'-Pt3Al was explained.The influence of alloying elements on ?'-Pt3Al was described.