Electrodeposition of Gold Alloys and the Mechanical Properties

Abstract

Strengthening of electrodeposited gold-based materials is achieved by alloying with copper according to the solid solution strengthening mechanism. Composition of the Au-Cu alloys is affected by the applied current density. The mechanical properties are evaluated by micro-compression tests to evaluate the mechanical properties in microscale to take consideration of the sample size effect for applications as microcomponents in MEMS devices. The yield strength reaches 1.15 GPa for the micropillar fabricated from constant current electrodeposited Au-Cu film, and the film is composed of 30.3 at% Cu with an average grain size of 5.3 nm. The yield strength further increases to 1.50 GPa when pulse current electrodeposition method is applied, and the Cu concentration is 36.9 at% with the average grain size at 4.4 nm.

Characterisation of Electroplated Gold Coatings for Dental Applications: Estimation of Thickness Using Non-Destructive Electron-Probe Microanalysis Related to Plating Time

“…Thus, highly predictable coating thicknesses can be obtained by varying the plating time. By keeping the voltage at 0.2 mA, the grain size of the plate ensures a high mechanical strength and enhanced durability [7].…”

“…Hardness and thickness of the coating have been identified as factors which are related to durability of the electrodeposited coating [2]. Mechanical strength, which is modulated by the grain size, will also affect durability [7]. The finer the grain size, the greater the mechanical strength of the deposit, both within it and in its attachment to the underlying metal substrate.…”

“…The finer the grain size, the greater the mechanical strength of the deposit, both within it and in its attachment to the underlying metal substrate. Grain boundary strength is therefore determined by grain refinement mechanisms [7]. Crystalline grain size is controlled by current density, bath temperature and the additive amount of the metal in the aqueous electrolyte.…”

“…Controlling current density is a practical way of controlling grain size and nucleation rate, with an increase in current density resulting in a finer-grained structure. However, a crossover is reached whereby an overpotential occurs, resulting in an increase in grain size [7].…”