A new technique has been developed for producing laminated composites of cyclic multilayered alloy (CMA) electrodeposits. The thickness and composition of the individual layers of the CMA deposits are altered precisely and conveniently by cyclic modulation of the cathodic current or potential during electrodeposition. It is thus possible to modify the structure to obtain laminated composite coatings which may have desirable engineering properties. Wear and corrosion resistances, mechanical hardness and strength, as well as certain magnetic, optic, and electronic properties of the plated composite alloys should be, in principle, straightforward to design and fabricate. The CMA technique was demonstrated by plating a wide variety ofAg-Pd CMA structures. Fine structures, with repeat distances as small as 0.05 ~m, were obtained. Both square and triangular waveforms were applied to produce sharp or gradual composition variations, respectively. The resulting deposits * Electrochemical Society Active Member. 1 Present address: MPI, Santa Clara, California 950,51. -~Present address: Oxy Metal Industries, Warren, Michigan 48089.

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Silver‐palladium alloys were electroplated as high quality coatings from a concentrated chloride bath. Adherent, uniform, and coherent deposits were obtained with thicknesses of up to 20 μm. The alloys were found to be homogenous, single‐phase solid solutions, with palladium content ranging from about 30% to 60%, depending on the operating variables. The microstructure of the plated Ag‐Pd alloys consists of very fine grains (100–300Å). These alloys have a fcc crystal structure, and the lattice parameter varies continuously with composition. The useful plating rate with moderate agitation was found to be about 0.44 μm/min at 10 mA/cm2, which is almost twice that of conventional cobalt‐hardened gold, due to the current efficiency of nearly 100%. Alloys containing about 40% Pd were obtained with these conditions. High speed plating of the Ag‐Pd alloy was achieved in a forced flow cell up to rates of about 9 μm/min. To achieve satisfactory deposits, it was generally necessary to use a thin (0.2–0.4 μm) soft gold underplating. Preliminary tests of electrical contact properties revealed that the Ag‐Pd coatings possessed low contact resistance (about 1 mΩ at 100g load). Other relevant properties include intermediate Knoop microhardness (about 200 kg/mm2 at 25g load) and an excellent resistance to formation of corrosion films in accelerated tests using flowers of sulfur. The present study indicates that the plated Ag‐Pd coatings are superior in contact resistance stability to the bulk wrought alloy R156 (40%Ag‐60%Pd). Finally, these coatings show satisfactory wear response in the selected tests provided a hydrocarbon lubricant is present.

Application of periodic reversal (PR) technique, in which a cathodic (depositing) step is followed by an anodic (polishing) step, was found very beneficial to the increase of electroplating rate of coherent niobium. With no mechanical agitation, the application of the PR technique facilitated an electroplating rate increase by a factor of about 10 over the direct current method. The morphology of the deposits was found to be of the columnar structure. The columns became more oriented along the [100] direction, and of smaller diameters as the rate of electrodeposition increased. Unexpectedly, beyond a certain rate and under certain conditions, the columnar grains became large once again. Under such conditions a pronounced heteroepitaxial effect of the substrate (Cu) grains on the deposit grain size and orientation was observed.