Ductile-brittle transition in steels irradiated with neutrons

Abstract The yield and fracture stresses of unirradiated and irradiated End steel have been measured at 20°, −78°, and −196°c. From the change in yield stress, [sgrave], (shear), with grain size, 2d, the values of [sgrave] i and kv in a Petch type equation, [sgrave]v=[sgrave] i +kv d −1/2, have been determined. The term kv is unaffected by irradiation to within 5% and [sgrave] i increases at a rate approximately proportional to the cube root of the dose. The effect of irradiation on the grain size transition from ductile to brittle fracture has been determined experimentally at -196°c and estimated from the change in [sgrave] i and the value of kv for tests at -78° and 20°c. The results are in accord with the predictions of Cottrell's relation ([sgrave] i d 1/2+kv ) kv =βγμ for the transition. The transition surface relating grain size, yield stress and temperature has been obtained.