In-situ high-energy X-ray characterization of neutron irradiated HT-UPS stainless steel under tensile deformation

The tensile deformation behavior of a high-temperature, ultrafine-precipitate strengthened (HT-UPS) stainless steel was characterized in-situ with high-energy X-ray diffraction at 20 and 400 degrees C. The HT-UPS samples were neutron irradiated to 3 dpa at 400 degrees C. Significant irradiation hardening and ductility loss were observed at both temperatures. Lattice strain evolutions of the irradiated samples showed a strong linear response up to near the onset of the macroscopic yield, in contrast to the unirradiated HT-UPS which showed a pronounced non-linear behavior well below the macroscopic yield. While the room temperature diffraction elastic moduli in the longitudinal direction increased after irradiation, the 400 degrees C moduli were similar before and after irradiation. The evolution of the {200} lattice strain parallel to the loading axis (epsilon(L)({200})) showed unique characteristics: in the plastic regime, the evolution of epsilon(L)({200}) after yield is temperature-dependent in the unirradiated specimens but temperature-independent in the irradiated specimens; and the value of epsilon(L)({200}) at the yield is an irradiation-sensitive, temperature-independent . parameter. The evolution of epsilon(L)({200}) corresponds well with the dislocation density evolution, and is an effective probe of the deformation-induced long-range internal stresses in the HT-UPS steel. (C) 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.