The low-temperature embrittlement of iron, iron alloys, and A212-B and modified Hy 80 steels in unirradiated and irradiated conditions was studied using the tension test. A radiation-induced transition temperature (embrittlement) at 125 to 130 K occurs only in irons with carbon content of about 30 ppm or greater. Embrittlement occurs with exposure as low as 2 X 1018 nvt and the embrittling temperature does not increase with exposure. This embrittlement is attributed to a carbon-vacancy defect formed by trapping of a carbon atom by a radiation-produced vacancy. Additions of substitutional alloys reduce this change in the embrittlement temperature.

No correlation has been found between the radiation-induced, low-temperature tensile embrittlement and the shift in notched impact transition temperature observed at higher temperatures.