Theoretical Study On Preferential Occupation Of Mn In B Containing Ni₃Al Alloy And Ni/Ni₃Al Interface And Their Properties

??-Ni₃Al is widely used in commercial alloys as a key strengthening component of nickel-based superalloys.However,its application is seriously affected by its low high temperature creep strength and intrinsic brittleness.Some studies have shown that adding Mn can improve the ductility of Ni₃Al.But for the occupation behavior of Mn in Ni₃Al,experimental results are different due to different experimental conditions and further research is needed.Because of B segregation at the Ni/Ni₃Al interface,the addition of B and Mn further enhances the composition range of the ductility of the alloy and the effect of B on the Mn occupation at the interface cannot be ignored.Therefore,the synergistic effect of B and Mn on the properties of Ni₃Al alloy and Ni/Ni₃Al interface has been considered in this study.In this paper,the first-principles method was used to study the relationship of the occupancy behavior of Mn in Ni₃Al before and after B doping with composition and temperature to further explore the effect of B and Mn co-alloying on the mechanical properties of Ni₃Al alloy.Then,the occupancy of Mn in the Ni/Ni₃Al interface and the B-doped Ni/Ni₃Al interface was investigated,and the effect of B and Mn on the stability of the Ni/Ni₃Al interface was analyzed.The conclusions are as follows:(1)Over the entire temperature range studied,B consistently occupies octahedral,but not tetrahedral,interstitial sites.Compared with the octahedral interstitial sites composed of Ni and Al atoms,B tends to occupy the octahedral interstitial sites composed entirely of Ni atoms.(2)The occupancy of Mn in Ni₃Al is affected by temperature and composition.In Ni₃Al alloys,Mn randomly occupies Ni sites or Al sites at 0 K.With the increase of temperature,in Al-rich alloys,the occupation of Mn prefers Ni sites to prefer Al sites;in normal stoichiometric alloys,it changes from randomly occupying Ni sites or Al sites to occupying Al sites;Ni-rich alloys,Mn always occupies the Al site.The addition of B suppressed the transition of Mn occupancy tendency.(3)Through the analysis of different structural mechanical properties,it is found that the ductility of all Mn-substituted Ni₃Al structures has been improved to varying degrees.In particular,both B and Mn,whether alloyed alone or simultaneously,enhance the ductility of Ni₃Al.(4)The addition of manganese enhances the stability of the Ni/Ni₃Al interface while the stability of the Ni/Ni₃Al system will decrease due to the lattice mismatch.In the Ni₃Al phase region,manganese occupies the aluminum sites in the range of lattice misfit.With the increase of lattice misfit,the occupation tendency of manganese changes from randomly occupying the nickel or aluminum sites to the aluminum sites with a weak tendency in the interface region Ni₃Al.(5)The stability of the Ni/Ni₃Al interface is further enhanced by boron doping.When the lattice mismatch is 4.4%,the occupation behavior of Mn in Ni/Ni₃Al interface region changes from occupying the Al sublattice to the Ni sublattice,however the occupation tendency is still weak.