The Effect Of Re On The Structure And Mechanical Properties Of Ni₃Al Intermetallic Compounds

In order to meet the requirements such as ultrahigh speed,long range,etc.,the high temperature in the combustion chamber will be caused in aero engines.Therefore,the research of materials for the hot end parts of engines has become a new direction.Ni₃Al intermetallics as a strengthening phase of nickel-based superalloys,has good high-temperature strength.Its high melting point and low density make it applicable for aero hot-end components.Besides,the addition of Re can enhance the strength and high temperature resistance of superalloys,and greatly improve the microstructure.So based on the first-principles calculation,the work analyzes the change of microstructure and mechanical properties of?'-Ni₃ Al after doping Re.About the change of microstructure,the results show that the energetically-favorable site of Re in Ni₃Al is Al replace site.Re doping causes a small increase in the lattice constant of Ni₃Al without causing serious lattice deformation.Analyses on differential charge density and state density show that Re atom bonds with neighboring atoms,especially with Ni atoms,and reduces the surrounding Ni-Al bond energy.Analyses on local state density show that Re atom has orbital interaction with the neighboring Ni and Al atoms,and the interaction with Ni is larger,which concerns the 5d orbit of Re and the 3d orbit of Ni.About the change of mechanical properties,the elastic constants calculating results indicate Re can cause increase of the stiffness and hardness of Ni₃Al.The Cauchy pressure value shows a slight improvement in toughness.With the increase of doping concentration,Re makes the stiffness and hardness better and decreases the ductility of Ni₃Al.By calculating the generalized stacking fault energy and fracture energy of the two slip systems[112^-]?111?and[11^-0]?111?of Ni₃Al,it shows that Re makes the slip system difficult to move and makes Ni₃Al difficult to fracture,which means the strength has increased.In the calculation of thermal properties,Re increases slightly the entropy of Ni₃Al and reduces slightly the Helmholtz free energy.Re increases greatly the bulk modulus of Ni₃Al at high temperature while reducing the thermal expansion coefficient of Ni₃Al at high temperature.This study will provide the theoretical data for improving the mechanical properties of single crystal turbine blades of aero-engines.