Annealing Effects on Mechanical and Transport Properties of Ni and Ni-Alloy Electrodeposits

The effect of annealing at temperatures up to 600 degC on the mechanical properties and the thermal and electrical transport characteristics of nickel and a nickel-manganese electrodeposits are presented. The samples include Ni plated from sulfamate salt with dodecyl sulfate surfactant and from NiSO₄ with saccharin additive and a NiMn alloy deposited from a nickel sulfamate bath with added MnCl₂. Recrystallization and grain growth, induced by annealing, are shown to strongly affect the mechanical and transport properties. Relatively coarse-grained Ni-sulfamate electrodeposits yielded properties closest to bulk Ni. The incorporation of sulfur (from saccharin additions to the plating electrolyte) or Mn into electrodeposited Ni produces materials with exceptionally fine grain size and with very high yield and ultimate strength. At the same time, the thermal and electrical conductivities are smaller than bulk Ni. Thermal annealing leads to a reduction in strength and an enhancement of the transport properties. The Ni-Mn alloy shows the best temperature stability of the mechanical and transport properties among the tested samples. The observed trends are explained in terms of the influence of microstructure on the mechanical and transport properties