Fe‒C alloys were electrodeposited at high current efficiencies from
FeSO4
solutions containing a dicarboxylic acid with a linear alkyl chain, represented by
COOH·false(CH2)normaln·COOH
(n = 0 to 7). The carbon contents of the deposits ranged from 0.1 to 3.7 weight percent (w/o), depending on the acid added to the bath. The hardness of the deposits sharply increased to a maximum value of HV 850 with increasing carbon content up to 0.6 w/o and progressively decreased at higher carbon contents. The deposits having carbon contents above 0.5 w/o exhibited a black color, because carbon‐rich alloys deposited through the black oxide films in a state similar to FeO containing an organic acid or its degradation products. Fe‒C alloy deposits had a body‐centered tetragonal, martensite‐type lattice with interstitial carbon atoms, and the axial ratios increased with increasing carbon content of the deposits. The high hardness of the Fe‒C alloy deposits is mainly attributed to the solid solution hardening by interstitial carbon atoms in the martensite‐type lattice. The larger grain size and FeO occluded in the bulk of the carbon‐rich deposits caused the decrease in hardness with increasing carbon content.
インバー合金電析膜の熱膨張特性
山本 貴代Thermal expansion properties of Invar (Fe-36 mass%Ni) alloy electrodeposits were investigated. The Fe-36 mass%Ni alloy electrodeposits from sulfate/chloride electrolytes using additives, saccharin sodium, and malonic acid. The electrodeposits, of about 150 μm thickness, had no crack. The thermal expansion curve showed that contraction of the electrodeposits occurred in the 270-420 ℃ range during first heating. During the first cooling and second heating, it showed the same behavior as that of melted Invar alloy. The coefficient of thermal expansion α (CTE) exhibited approximately α=10×10 -6 /℃ for the as-deposited electrodeposits and approximately α=1×10 -6 /℃ for electrodeposits annealed above 500℃ . The CTEs of the electrodeposits annealed above 500 ℃ showed excellent agreement with that of the melted Invar alloy. The decrease in the CTE resulted from the increase of the fcc phase in the electrodeposits caused by heat treatment.Invar alloy electrodeposits are anticipated for application to high-definition electroformed products with low CTEs.
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