ABSTRACT
Investigations showed that deformation proceeded without twinning, beginning with
a rise to a certain temperature. A l so , increase of the deformation temperature promoted
block formation. The latter process consisted of dividing of the grains into a few large
blocks within a grain and simultaneously of a great number of fine blocks formed along the
grain boundaries. After the fine block formation, the grain boundaries became of serrated
appearance. Another process which became more important with temperature increase was
sliding along the grain boundaries. This process was recognised to be a cycl ic one with
alternate grain boundary migration in every cycle. Decrease of the deformation rate
promoted the high temperature mechanisms of deformation to act at lower temperatures.