FAST-NEUTRON IRRADIATION HARDENING OF AUSTENITIC STAINLESS-STEEL AT 250-DEGREES-C

Tensile specimens of solution annealed and cold-worked 316 and PCA type austenitic stainless steels were irradiated in the HFIR, HFR and R2 reactors, to 3.1-10.9 dpa at 523 K. Earlier reported tensile curves are reviewed and analyzed on remaining homogeneous strain hardening. The yield stresses of solution annealed 316L and PCA reached a plateau level of about 820 MPa at 6 dpa. Radiation hardening of similar steels in cold-worked condition - 20%CW 316 and 25%CW PCA - saturated at 1040 MPa. Uniform elongation of the annealed steels gradually decreased from 12% at 3.1 dpa to 3% at 10.9 dpa. The cold-worked steels lost their remaining strain hardening capability within 3 dpa. A tentative correlation between yield stress and uniform elongation, suggests an upper yield stress limit of about 850 MPa to occurrence of homogeneous plastic flow at 523 K.