The ductile-brittle transition in the fracture of α-iron: I

Abstract A criterion for the transition in fracture mode from ductile to cleavage is calculated for fracture at a notch. It is concluded that the temperature-dependence of this transition probably arises more from that of the Peierls-Nabarro stress required to move a free dislocation in α-iron than from the temperature-dependence of the locking of e dislocation source. The transition temperature is found to be a function of grain size, the friction on a free dislocation, the strength of the dislocation locking, the degree of triaxiality of the applied stress and the elastic constants.