Temperature and particle size effects on flow localization of 9-12%Cr ferritic/martensitic steel by in situ X-ray diffraction and small angle scattering

Radiation-induced defect structures are known to elevate material yield strength and reduce material ductility so that small strains induce plastic instability. This process is commonly known as flow localization. Recent research indicates that the flow localization in face-centered cubic (FCC) materials is controlled by critical stress, the true stress at the onset of necking. Critical stress is found to be independent of irradiation dose, but have strong temperature dependence. Here simplified 9-12% ferritic/martinsetic steels are examined using X-ray diffraction and small angle scattering under in situ tensile deformation, in order to elucidate the controlling mechanisms and temperature dependence of critical stress. It is found that the critical stress for the onset of necking is linearly correlated with critical interfacial strength, which in turn determines the void nucleation. The effects of temperature and particle size on critical stress are correspondingly determined by how temperature and particle size influence the critical interfacial strength.