Stored energy of a severely deformed interstitial free steel

A Ti-stabilised IF steel subjected to room temperature equal channel angular pressing (ECAP) for 8 passes, route BC was further cold rolled to 25, 50 and 95% thickness reductions. The evolution of bulk stored energy (350–600 J mol−1) and the associated thermal behaviour was investigated by differential scanning calorimetry (DSC). Local stored energy (5–140 J mol−1) was measured using microhardness, electron back-scattering diffraction (EBSD) and X-ray line profile analysis. The higher stored energy values via calorimetry correspond to energy release from all sources of strain in the material volume as well as Ti precipitation during annealing. An apparent activation energy of 500–550 J mol−1 suggests sluggish recrystallisation due to excess Ti in solid solution.