Nature of Superplastic Deformation

As known, there was made a number of hypotheses for the nature of superplastic (SP) deformation and many physical models of this phenomenon were suggested [1-2]. The majority of authors tried to explain the σ=σ(e) dependence on the basis of a mechanism of SP deformation. And though their concepts on diffusion creep or dislocation slip in combination with grain boundary sliding were absolutely different, the final constitutional equations were rather similar differing only by coefficients [1-2]. It is not wonder since the experimental dependence σ=σ(e) was studied rather thoroughly and its parameters are known. However, the theory of SP deformation should explain not only the phenomenology but also all structural features of material during SP flow. It is also very important to predict and explain new effects, such as low temperature and high strain rate superplasticity. The aim of the present work is to investigate the main mechanism and characteristics of diffusion processes during SP deformation, and to develop a physical model of this phenomenon. The review of experimental data on superplastic alloys and model materials [3-10] obtained recently in the Institute for Metals Superplasticity Problems (IMSP) of the Russian Academy of Sciences is presented in this paper.