To analyze the thermal expansion behavior of the material system with various phases such as bi-dispersed composites, many metallurgical parameters such as the size, shape, elastic modulus, and volume fraction of each phase in the system should be considered. In this study, a new approach was attempted to understand the effect of the metallurgical parameters on the linear coefficient of thermal expansion (CTE). In this metallurgical approach, it was considered that during cooling the relaxation of residual stresses create elasto-plastic deformation zone around ceramic hard phases and crystallized phases in the soft metal matrix. The size of reinforced phases and other metallurgical factors of matrix alloy or composite system were also considered. The interacting effects among the reinforced hard phases, the crystallized phases and the soft matrix were considered by introducing the influence of the elasto-plastic deformation zone around each phase, which is distinguished from the previous approaches. According to this theoretical approach, it was revealed that the linear CTE of material system with various phases are influenced by the size of the effective plastic region and reinforced phases as well as the volume fraction, the shape, the elastic modulus, and Poisson's ratio of each phase. (C) 2003 Elsevier B.V. All rights reserved.