First principles study of Al and Ni segregation to the α-Fe/Cu (1 0 0) coherent interface and their effects on the interfacial cohesion

The first-principles method is used to characterise the segregation behaviours of aluminium and nickel at the interfaces of copper precipitates in ferritic steels. We find the segregation of aluminium and nickel at interfaces of copper precipitates are both energetically favourable. The main contributor to segregation energies of aluminium and nickel are the strong bonding energy of aluminium and nickel at the interface of copper precipitate, respectively. We also find their segregation energies depend on the composition of copper precipitate. Furthermore, we investigate the influences of segregation on interfacial cohesive properties for copper precipitates in ferritic steels. The interfacial cohesion of copper precipitates is enhanced by aluminium segregation but reduced by nickel segregation. Opposite roles derive from the different symmetrical features of valence state for aluminium and nickel.