Effect of AI on the Hot deformation of Ferrite in Cu-Mn Steels.

Effect of small Al additions, from 0.14% to 0.31% AI, on
the hot deformation behavior of low carbon steels
containing 1%Cu-1.2%Mn was investigated In the
temperature range of 750-800•C over the strain rate range
of 1O.3.1O.1s•1 by a hot compression testing machine. The
flow curves obtained, exhibited typical characteristics of
dynamic recovery type of softening mechanism, and the
critical strain to steady stat e flow and the steady state flow
stress decreased with increasing temperature and /or
decreasing strain rate . Furthermore, increasing AI
additions, led to higher critical strains and higher flow
stress levels and dynamic recovery was retarded. This
effect of AI, in the presence of Cu and Mn alloying
elements, is contrary to the previous reports on the
individual effect of AI, showing promotion of dynamic
recovery with increasing Al content in low carbon steels.
Scanning electron microscopy study of final
microstructure showed that deformation of initial grain
structure into a pancaked shape, formation of more or
less equiaxed subgrains, and dynamic precipitation of
second phase particles on the grain boundaries, as well as
the subboundaries were the main microstructural changes
associated with hot deformation of steels under
consideration in ferrite phase region.