電析Ni-Pめっき皮膜の硬度増加挙動に対する一考察 (非晶質めっきの作製法とその応用<特集>)

概要

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Heating causes the hardness of Ni-P plated films to increase, reach a maximum, and then decrease. This phenomenon is also observed in nickel films of low phosphorus content deposited from nickel sulfamate-hypophos-phorous acid solutions. To explain the hardness with heating, the peak profiles of X-ray diffraction patterns were analyzed, and the crystal grain size and residual internal strain were calculated. The relationships between these and hardness change were discussed. Films deposited from baths containing nickel sulfamate and 0 to 2.5g/L hypophosphorus acid were heat treated up to 450°C. Nickel crystal grain size in the (100) direction and residual internal strain were calculated from the Ni(111) and Ni(200) peak profiles obtained by X-ray diffraction. TEM observation was also conducted.It was found that 1) The hardness of nickel films containing phosphorus is based on the solid solution effect of phosphorus, and it increases with phosphorus content; 2) The change in hardness with heating is caused by segregation of phosphorus as the pre-stage of Ni3P precipitation; 3) The decrease in hardness at higher temperatures is caused by recrystallization and by stress release with Ni3P precipitation.
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