This paper uses a combination of thermodynamic calculation and kinetic simulation to model the homogenisation process of cast microstructure for multi-component alloys. The approach assumes that the solute segregation profile across the half dendrite arm spacing can be scaled to the solute concentration profile during solidification as generated by a Scheil type calculation. When secondary phases dissolve during homogenisation, they are treated as an additional fraction of pseudo-eutectic to the initial solute concentration profile of the primary solution phase. The methodology is compared with the assumptions made by other authors, highlighting the significant advantages in the present treatment. Examples are drawn from a cast nickel-based superalloy.