A Model for Superplasticity not Controlled By Grain Boundary Sliding

It is commonly assumed that grain boundary sliding can control plastic deformation in fine grained crystalline solids.  Superplasticity is often considered to be controlled by grain boundary sliding, for example.  I have never accepted that view, though my own opinion is very much at odds with the commonly accepted picture.  When I was asked to write a paper in honor of Professor F.R.N. Nabarro's 90th birthday (Prof. Nabarro subsequently died shortly after his 90th birthday), in the early part of 2005, I decided to resurrect a paper that my former student Merrilea J. Mayo and I had written nearly 20 years ago based on her Ph.D. dissertation work. We submitted the attached paper for the Nabarro volume but it was not accepted for publication.  The reviewers would not accept the basic assertion of the paper that superplasticity is not controlled by grain boundary sliding.  The reader is thus warned that the attached paper is controversial and very much at odds with prevailing views on superplasticity and grain boundary sliding.  It is presented here in the hope that discussion of these issues might be stimulated. - W.D. Nix