Deformation twinning and its possible influence on the ductile brittle transition temperature of ferritic steels

The occurrence of deformation twins in the ductile-to-brittle transition (DBT) temperature region of technically pure polycrystalline bcc Fe was observed under different testing conditions. Based on the results of mechanical tests, scanning electron microscopy and fractographical analysis, it is proposed that in the transition region of polycrystalline bcc Fe a mechanism of cleavage can operate, which is similar to that proposed by Biggs, Pratt and Hull for single crystals at cryogenic temperatures. The occurrence of deformation twins at DBT temperature was also proved in three ferritic structural steels. These results imply that deformation twinning could possibly play a significant role in the DBT of some polycrystalline ferritic structural steels as well.