Abstract: The Ni-W gradient deposit with nanostructure was prepared by controlling the bath temperature and current density. The plating bath contained sodium tungsten, nickel sulfate and citrate, and the preparation was undertaken at various current densities. X-ray diffraction (XRD) and energy dispersive X-ray analysis (EDX) indicate that crystallite size of the deposit decreases from 10.9nm to 1.5nm and lattice strain increases with the increase of W content in the direction of deposition. The structure of the deposit changes from crystalline to amorphous gradually with associated increase in lattice strain. These show that the deposit is gradient with nanostructure. Furthermore, the strain distribution in the Ni-W gradient deposit studied by the digital-image correlation method can eliminate the mismatch of expansion coefficients at the interface, thus relaxing the thermal stresses of the materials.

Key words: Electrochemical deposition, Ni-W alloy, Nano-gradient