Microstructural observations revealed that increase in volume fraction of SiC particles lower the coefficients of thermal expansion (CTE) of the composites, and the CTE of metal matrix composites is proportionally changed with the size of Si phase. To analyze the thermal expansion behavior of aluminium composites, a new model for the CTE of monodispersed binary composites on the basis of Ashelby`s cutting and welding approach was introduced. In this theoretical model, it was considered that during cooling relaxation of residual stresses can create elastoplastic deformation zone around a SiC or Al₂O₃ particle in the matrix. Size of reinforced particles and other metallurgical factors of matrix alloy and composites were also considered. In this model, the interacting effect between the reinforced hard particle and soft matrix is considered by introducing the influence of the elastoplastic deformation zone around a particle, which is distinguished from the Kerner`s model. It was revealed that the CTEs of composites are influenced by particle volume fraction, elastic modulus and Poisson`s ratio as well as elastoplastic deformation zone size and particle size.