Abstract
The appearance of deformation twins in the wide temperature region of three structural ferritic steels was analyzed. It was found that the deformation twinning was associated with cleavage fracture. These results were verified in more detail on technically pure bcc Fe. For two grain sizes the tensile tests at two different strain rates and impact tests proved deformation twinning in the transition region of technically pure bcc Fe. In ductile specimens the deformation twinning was not observed. The fractographic analysis of cleaved specimens proved the reinitiation of cleavage on the twin boundary. Based on the experimental results, a linkage between the transition temperature and deformation twinning in ferritic steels can be assumed.

Key words
deformation twinning, ductile-brittle transition temperature, cleavage crack initiation, ferritic steels

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