The effect of prestrain at room temperature on the relationship between non-ductile transition temperature and tensile speed has been examined on a low carbon steel.
The results obtained are summarized as follows.
(1) The transition temperature of the prestrained specimen rises with increasing prestrain at room temperature.
(2) The relation between the transition temperature TB and the tensile speed V is represented by the following equation,
where a is dependent on the amount of prestrain and b is a constant.
(3) There are little deformation twins in the prestrained specimen tested in the vicinity of its non-ductile transition temperature. The micro-cracks remain slightly in the prestrained specimen tested at a low tensile speed but they disappear at a high tensile speed.
(4) A number of results seem to support the dislocation piled-up mechanism of the cleavage fracture.