ИСТИНА

Superplasticity is a regime of materials deformation, in which the huge values of strain can be achieved in absence of microstructural defects. The properties of superplastic flow strongly depend on microstructural state of the material. During the deformation, several microstructure mechanisms are working together, which leads to both grain growth and grain refinement as a result of newly appeared grain boundaries. Experimental data commonly used in superplasticity can be described by phenomenological constitutive equations of different types, such as creep, viscoplasticity, etc. Determination of parameters values in the systems of constitutive equations is usually done by means of the special algorithm for the particular system. The authors of the present work suggest more universal algorithm of parameters values determination suitable for some class of superplastic constitutive equations. The approach to check the stability of the approximation to the random errors in the experimental data is described. The model of grain refinement, which is based on the concept of partial refinement of the grains groups, is also suggested. Extended experimental data with grain sizes distributions is than used to build a model describing the specific features of microstructure evolution during the superplastic deformation. Applicability of the developed model is shown on the example of blowing the sphere by pressure.