A simplified diagram of the phenomenon of pore formation in superplastic deformation of two-phase materials is constructed. Based on the diagram, a simple quantitative criterion is proposed. By means of the criterion the presence (or absence) of pores can be predicted from a relationship between the strength of the phases. It is known [1,2] that two-phase (and, in fact, multiphase) materials are distinguished by increased stability of the fine-granular structure, a factor which is essential for realization of superplastic deformation. Thus, two- and multiphase materials can be successfully used in processes of superplastic working of sheet bars [3-5] where reliable support of the required plastic life at relatively low strain rates is necessary.
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