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.