First Principles Study On Properties Of Ni-X(Mo?Sn) Binary Compounds

Intermetallic compound is a kind of important high temperature structural materials.It is widely used in aviation,aerospace,chemical,electronics and other fields.However,its low plasticity and low fracture toughness of faults severely limit the practical application.In addition,with the rapid development of the application domain,the higher requirements have been put forward for comprehensive performance of intermetallic compounds.Therefore,the study of improving its comprehensive performance is important and great significance.In this paper,the properties of Ni-X?X = Mo,Sn?binary intermetallic compounds are studied.Ni-Mo binary compounds(Ni₂Mo?Ni₃Mo(DO₂₂)?Ni₃Mo?DOa??Ni4Mo)and Ni-Sn binary compounds?m C14-Ni₃Sn4?o P20-Ni₃Sn2 ?h P4-Ni₃Sn2 ?c F16-Ni₃Sn?h P8-Ni₃Sn?c P4-Ni₃Sn?were analyzed by first principle calculation based on the density functional theory method.Using CASTEP software package,first of all,we calculated the lattice constants?cell volume?cell total energy?elastic constants?elastic modulus?poisson's ratio?lame constant?hardness and density of states under zero pressure.Second,we studied structural stability,mechanical,electronic properties of Ni-X?X = Mo,Sn?binary compounds with pressure.The results reveal that the calculated lattice parameters and elastic constants of various compounds at zero pressure are agreement well with the available experimental values and others theoretical datas,showing that calculation method is feasible.All formation enthalpy are negative,indicating that can form stable compounds.For the Ni-Mo binary compounds,the comprehensive performance of the stable phases is higher than that of the metastable phases.For Ni-Sn binary compounds,c P4-Ni₃ Sn has the greatest elastic modulus and hardness,and c F16-Ni₃ Sn has the best ductility?plasticity and anti-compression ability.For the Ni-Mo binary compounds,the values of V/V₀ decrease with pressure and the rates of change decrease gradually.The formation enthalpy decrease with pressure.Thus high pressure can improve the ability of alloying.The calculated results of bulk modulus B?shear modulus G?Young's modulus E?Lama constant ? and Hardness H illustrate that pressure can improve the resistance to deformation ? compression resistance and hardness of four compounds.In addition,ratio of bulk modulus to shear modulus B/G and poisson's ratio ?represent that all compounds are ductile materials.The state density is also analyzed to explain the physical origin of the pressure effect on four compounds.Thus suggests that increasing pressure can improve the stability and hardness of all compounds.For Ni-Sn binary compounds,the values of relative V/V₀ are decreased to be slight with incresing in pressure.The formation enthalpy is negative,and is decreased with pressure.Thus compounds are easier to form and high pressure can improve the ability of alloying.The anti-volume deformation ability,resistance to shear strain capacity and the stiffness of all compounds except for c F16-Ni₃ Sn increase with pressure.Appropriate pressure can improve the ductility ?plasticity and hardness of six compounds.On the analysis of the density of states,the results show that Fermi level of state density value is reduced with pressure,which indicates that increase pressure can improve the comprehensive mechanical properties of the compounds.