Changes in internal energy associated with recovery and recrystallization in iron silicon alloys and pure iron

The release of energy in Fe-5.6 at. % Si single crystals and Fe-6.1 at. % Si polycrystalline specimens deformed by cold-rolling was found to occur in two distinct stages on heating at a rate of 2.5°C/min. The evolution of energy in the first stage was 1 ~ 1.6 calg in a range of 100–300°C and was associated with increase in electrical resistivity, microhardness and flow stress, and with decrease in lattice parameter. In the second stage, the evolution of energy was 2.3 ~ 6.3 calg in a range of 300–750°C and was associated with gradual decrease in the above physical quantities. In cold-rolled Fe, the energy was evolved in one stage corresponding to the second stage in Fe-Si. It is very probable that the energy evolution in the first stage is due to rapid re-ordering which was assisted by excess vacancies produced by cold-rolling. The second stage is probably due to annihilation of dislocations followed by the formation of subgrains and their initial growth.