| 摘要 |
Bipolar (pulse reversal) current, with both positive and negative current portions, is used to electrodeposit a nanocrystalline grain size deposit. Polarity Ratio is the ratio of the absolute value of the time integrated amplitude of negative polarity current and positive polarity current. Grain size can be precisely controlled in alloys. The deposit exhibits superior macroscopic quality, being relatively crack and void free. Parameters of current density, duration of pulse portions, and composition of the bath are determined with reference to constitutive relations showing grain size as a function of deposit composition, and deposit composition as a function of Polarity Ratio. The parameters can be used to select a specified grain size. Coatings can be in layers, each having an average grain size, which can vary layer to layer and also in a region in a graded fashion. |
