In situ backscattered electron imaging study of the effect of annealing on the deformation behaviors of Ni electroformed from additive-free and saccharin-containing sulfamate solutions
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The Ni samples were electroformed from additive-free (AF) and saccharin-containing (SC) sulfamate solutions, respectively. In situ backscattered electron (BSE) imaging, electron backscatter diffraction (EBSD), and electron-probe microanalysis (EPMA) were used to investigate the effect of annealing on the deformation behaviors of the AF and SC samples. The results indicate that columnar grains of the as-deposited AF sample had an approximated average width of 3 μm and an approximated aspect ratio of 8. The average width of columnar grains of the as-deposited SC sample was reduced to approximately 400 nm by the addition of saccharin to the electrolyte. A few very-large grains distributed in the matrix of the SC sample after annealing. No direct evidence indicated that S segregated at the grain boundaries before or after annealing. The average value of the total elongations of the SC samples decreased from 16% to 6% after annealing, whereas that of the AF samples increased from 18% to 50%. The dislocation recovery in grain-boundary areas of the annealed AF sample was reduced, which contributed to the appearance of microvoids at the triple junctions. The incompatibility deformation between very-large grains and fine grains contributed to the brittle fracture behavior of the annealed SC Ni.
Keywordsbackscattered electron imaging annealing electroformed Ni sulfamate solution deformation behaviors
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This work was financially supported by the China Scholarship Council (No. 201606460015). The authors also appreciate the support of the H. Nakano laboratory of Kyushu University for the study.