Microstructural Evolution and Internal Friction Behavior of a Ferrite/Martensitic Steel Induced By Equal-Channel Angular Pressing

newly developed equal channel angular pressing (ECAP) route B C-UD2 was applied to extrude the Fe9Cr1.5W0.7Si (in weight) ferrite/martensitic steel, and the microstructural evolution and its effect on the internal friction (IF) behavior were investigated systematically. Microstructural characterization indicates that the initial ferrite/martensitic structure was broken into a fine laminar structure with a roughly 45 deg inclination to the extrusion direction (ED), and the corresponding initial weak Goss and ⟨ 111⟩∥RD texture evolves into typical extrusion fibers b1, b2, and b3. At the same time, M 23 C 6 and MX phases were partially dissolved after extrusion, which leads to a decrease in the Zener–Smith dragging force. Combined with the high stored energy produced by ECAP, both of them induced the decrease of recrystallization temperature and the increase of interfacial migration density during recrystallization, as revealed by the high-temperature IF behavior. In particular, the intensity variation of the recrystallization peak is also consistent with the hardness variation during annealing. The correlation between microstructure characterization results and IF behavior reflects the accuracy and reliability of the IF technique for the study of recrystallization behavior of structural materials in nuclear reactors.