電着亜鉛-鉄合金の結晶形態と微細構造

概要

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Zinc-iron electrodeposited sheet steels have been widely adopted for automobile bodies for their improvements in the corrosion resistance and paintability. In principle, these properties depend on the crystal structure, morphology and microstructure of deposits. The deposits of various zinc contents have been prepared galvanostatically from sulfate baths and examined by scanning and transmission electron microscopes. The 99.5 at% zinc, η-single phase deposit exhibits a collective morphology of hexagonal plates thin in the direction of c-axis. With the increase of iron content, the Γ-phase forms in addition to the η-phase. The η-phase plates stack in the direction of c-axis and form the hexagonal columnar crystals which have triangular pyramidal shapes in morphology. The Г-particles disperse within the grain and along grain boundaries of these η-phase plates. The Burgers orientation relationship holds between the η-and Г-particles. The 91.2 at% zinc hexagonal columnar crystals form steps on {10.0}_η surfaces. An increase of iron content to 85.1 at% zinc, however, flattens the steps on {10.0}_η surfaces. Further increase of iron content to 73.0 at% zinc produces a large amount of Г-particles, which cannot be absorbed any more within the η-phase. These excess Г-particles form granular crystals, and precipitate between the hexagonal columnar crystals.
社団法人日本鉄鋼協会の論文
1988-12-01