RESUMO
To assess the individual and synergistic effects of 2-butyne-1,4-diol (BD) and chloride ions on the microstructure and residual stress of electrodeposited nickel, various nickel layers were prepared from sulfamate baths comprising varying concentrations of BD and chloride ions by applying direct-current electrodeposition. And their surface morphologies, microstructure, and residual stress were tested using SEM, XRD, EBSD, TEM, and AFM. While the nickel layers composed of pyramid morphology were prepared from additive-free baths, the surface flattened gradually as the BD concentration of the baths was increased, and the acicular grains in the deposits were replaced with <100> oriented columnar grains or <111> oriented nanograins; additionally, the residual tensile stress of the deposits increased. The addition of chloride ions to the baths containing BD significantly increased the residual stress in the nickel layers, although it only slightly promoted surface flattening and columnar grain coarsening. The effects of BD and chloride ions on the growth mode and residual stress of nickel deposits were explained via analysis of surface morphologies and microstructure. And the results indicate that the reduction of chloride ion concentration is a feasible way to reduce the residual stress of the nickel deposits when BD is included in the baths.
RESUMO
In this paper, we report an in situ study regarding the microstructural evolution of a nickel-based alloy with high proportional twin boundaries by using electron backscatter diffraction techniques combined with the uniaxial tensile test. The study mainly focuses on the evolution of substructure, geometrically necessary dislocation, multiple types of grain boundaries (especially twin boundaries), and grain orientation. The results show that the Cr20Ni80 alloy can be obtained with up to 73% twin boundaries by annealing at 1100 °C for 30 min. During this deformation, dislocations preferentially accumulate near the twin boundary, and the strain also localizes at the twin boundary. With the increasing strain, dislocation interaction with grain boundaries leads to a decreasing trend of twin boundaries. However, when the strain is 0.024, the twin boundary is found to increase slightly. Meanwhile, the grain orientation gradually rotates to a stable direction and forms a Copper, S texture, and α-fiber <110>. Above all, during this deformation process, the alloy is deformed mainly by two deformation mechanisms: mechanical twinning and dislocation slip.
