Fracture in Complex Microstructures

This paper reviews fracture features of a variety of conventional and advanced materials which consist of more than two different phases in terms of composite material. To be concrete, the materials include ductile cast irons, carburized steels, aluminum alloys, and several kinds of discontinuously-reinforced composites. all of which have been studied by the present authors to date. Firstly, features on fracture of the above-mentioned three conventional materials are introduced. Those have constructions common to artificial composites: particle reinforced composite and layered composites. In the latter half of this paper, the detailed mechanisms of deformation and fracture in artificial composites and those analyses mainly on the basis of continuum mechanics and fracture mechanics are shown. Deformation and fracture behaviors of "natural" (or in-situ) and artificial composites are discussed in terms of their similarities and discrepancies both from metallurgical and mechanical points of view in order to bring systematic understanding of the materials having complex microstructures. In addition, it is shown that certain phenomena that already constitute common knowledge in the field of composite materials, should be strongly considered in the field of conventional materials.