抄録
The equilibrium composition of the solid phase differs in general from that of the liquid phase, and segregation may occur which the composition of the solid phase formed at different times differs from the bulk compositions.
In the case of the β→α transformation in nickel aluminium bronze castings, as well as in the solidification of solid solution, the composition of the coexisting β and α phase have to change continuously. But the change requires diffusion, which at ideal condition remains incomplete in α phase, since the diffusion rate in α phase are comparatively low. So non-equilibrium eutectoid remains in the alloy containing 9 to 10% aluminium and 5% each of nickel and iron.
Theoretical approach has been also made for the degree of segregation which depends on the factors of the nucleation rate of the α phase.
It has been shown that under slow cooling conditions significant segregation can be expected if the nucleation rate is low.
