Recrystallization behavior of SPD processed high purity iron was studied. The 99.95%
iron sheet was deformed by the accumulative roll-bonding (ARB) process up to 8 cycles (equivalent
strain of 6.4) at ambient temperature. Subsequently, the ARB-processed specimens were annealed for
1.8ks at various temperatures from 300°C to 500°C. The microstructures of these specimens were
characterized by TEM and SEM/EBSP. The microstructure of the as-ARB-processed specimens
showed the lamellar boundary structure elongated along RD, which was the typical microstructure of
the ARB-processed materials. The mean interval of the lamellar boundaries was about 100 nm. After
annealing at 400°C, the ARB specimen showed a partially recrystallized microstructure composed of
equiaxed grains with grain size larger than 10 5m and the recovered lamellar boundary structure.
After annealing above 500°C, the microstructures were filled with equiaxed recrystallized grains.
These results suggest that conventional discontinuous recrystallization characterized by nucleation
and growth occurs during annealing at annealing temperature above 400 °C. In previous work
reported about the annealing behavior of the low carbon IF steel ARB processed, the continuous
recrystallization occurred during annealing at annealing temperature above 600 °C. The
recrystallization temperature of the pure iron was much lower than the IF steel and the
recrystallization process were significantly different. This difference was suggested to be caused by
inhomogeneous microstructure in the pure iron ARB-processed.
Preparation of High Purity Iron and Its Recrystallization Temperature
