Bolt samples of PH13-8Mo were irradiated to doses of 0.5, 1 or 2dpa. The microstructure was investigated with transmission electron microscopy and its evolution was considered with reference to the mechanical properties. The PH13-8Mo was a precipitation-hardened martensitic steel, but a large amount of austenite was also observed. The precipitation hardening resulted from the formation of small coherent NiAl precipitates in the martensite phase. Their size, size distribution and density were found to be unaffected by neutron irradiation. The dislocations in the martensite phase were mainly a/2<111> type screw dislocations whereas, in the austenite phase, they were mainly a/2<110> type screw dislocations. The line dislocation structure did not change during irradiation, but small irradiation induced defects were observed. Using the Orowan model, it was argued that the latter were responsible for the irradiation hardening.

Defect Structure of Irradiated PH13-8Mo Steel. W.Van Renterghem, A.Al-Mazouzi, S.Van den Berghe: Journal of Nuclear Materials, 2007, 360[2], 128-35