A numerical simulation of nickel segregation in castable superinvar alloys has been carried out. A relationship has been revealed between the linear thermal expansion coefficient and the pattern of nickel distribution over the cast structure components. The results obtained make it possible to determine a region of compositions providing optimum thermal properties of the invars, as well as to vary the linear thermal expansion coefficient according to the known regularities by directional action on the degree of segregation of the alloy's components.