Effect of Heat Treatment of Electrodeposited Ni-Sn Alloy on Its Hardness and Structure

Electrodeposition of Ni-Sn alloy has recently become the object of remarkable attention, for the deposit obtained is of high hardness and has excellent properties such as to prevent corrosion, etc. The structure and properties of this alloy deposit differ from those of the alloy of the same component prepared by casting. Therefore, a series of experiments to study the effect of heat treatment upon hardness and hardness of the alloy deposit was carried out, and the result was as follows: 1. The component of Ni-Sn alloy deposit obtained from chloride-fluoride electrolyte is around 65% Sn and 35%Ni, and the structure is single phase of solid solution and hexagonal similar to γ (Ni3Sn2), while the structure of the alloy of the same component prepared by casting is a mixture of two intermetallic compound γ (Ni3Sn2) and δ1 (Ni3Sn4) phase. 2. As plated, the deposit has the (1120) plane parallel to the base metal and the (0002) plane vertical to the base metal corresponds to slip or cleavage plane, along which cracks easily occur or sometimes the deposit is broken. 3. The hardness of the deposit increases by two steps with an increase of temperature of heat treatment. 4. As well as hardness, the structure of the deposit is also affected by heat treatment; at 300°C a part of δ1 phase precipitates from solid solution and above 700°C it decomposes completely into γ and δ1 phases.