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The influence of current density and saccharin concentration on nanocrystalline nickel coatings synthesized by direct current electrodeposition was systematically analyzed. For current densities ranging from 0.5 A/dm2 to 1.5 A/dm2, nanocrystalline nickel with broad microhardness distribution ranging from 415 Hv to 603 Hv could be synthesized by adjusting saccharin concentration. The preferred orientation in the deposits existed at 0.5 A/dm2 and changed progressively from a (111), (200) double orientation texture to a (200) orientation texture as saccharin concentration increased. The internal stresses of the samples at 0.5 A/dm2 decreased to nearly 0 MPa as saccharin concentration increased to 1.2 g/L. The results of DSC curves show that the samples grew until 600 癈 and were stable near to bulk nickel when grain size ranged from 28 nm to 98 nm. However, when grain size was 10 nm, the samples initially grew abnormally at 317 癈. Moreover, thermal stability decreased sharply.