Temperature dependence of strengthening mechanisms in the nanostructured ferritic alloy 14YWT: Part I-Mechanical and microstructural observations

This paper presents experimental results on the mechanical and microstructural behaviors of the nanostructured ferritic alloy 14YWT and provides discussion relevant to deformation mechanisms over a wide range of temperature. The temperature dependence of strength was investigated over a wide temperature range of -196 to 1000 °C. Detailed microstructural characterization before and after deformation was conducted to obtain the key information on deformation mechanisms; microstructural information before and after tensile deformation, including crystallographic texture, dislocation structures, and nanoclusters, was obtained from the focused ion beam lift-out specimens using EBSD, TEM, and APT techniques. Multiple deformation stages could be identified in the yield strength versus temperature curve. The dislocation structures in the specimens deformed at room temperature and at 900 °C were found to be significantly different. EBSD results were used to elucidate changes in the crystallographic textures of the specimens before and after deformation at 900 °C.