In-situ study of initiation and extension of nano-thick defect-free channels in irradiated nickel

Radiation defects-induced plastic flow localization is the origin of loss of ductility in irradiated metals.Defect-free channels(DFCs)are a typical form of strain localization that lead to crack initiation and premature failure.A comprehensive understanding of the DFC dynamics is key to managing radiation boosted property degradation.Despite great research efforts,a clear mechanism of DFC remains unknown.Here,our in-situ tests on irradiated Ni pillars provide a real-time observation of the dynamics of DFCs,including DFC initiation,extension and thickening.The merging and spreading of dislocation loops serve as an alternative mechanism of dislocation sources that emit massive dislocations and initiate nano-thick DFCs inside the grain.Nano-thick DFCs were formed through chopping up or sweeping away of loops by mobile dislocations.Annihilation of opposite loops and interactions between loops and vacancies accelerate DFC extension.Activation of multiple dislocation sources and dislocation cross-slips are the mechanisms for DFC thickening.

Interface-facilitated stable plasticity in ultra-fine layered FeAl/FeAl_(2) micro-pillar at high temperature

Fe-Al compounds possess a combination of high strength and corrosion resistance at high temperatures.However,increasing Al content to make them lighter results in embrittlement.Here,we investigate the high-temperature behavior of a novel,lightweight,ultra-fine-layered FeAl/FeAl_(2) material.We report a transition from unstable to stable plasticity at 450℃.Below 450℃,deformation is dominated by localized shear deformation within the soft FeAl layers,while above 450℃,it proceeds by co-deformation between Fe Al and the brittle FeAl_(2) layers.We show that co-deformation is associated with the temperature at which the interface converts from sliding to sourcing dislocations for Fe Al_(2).