Mechanical and Structural Characteristics of Electrodeposited Ni–Fe–W Alloy after Heat-Treatment

Ni–Fe–W alloys were obtained by electroplating using an ammoniacal citrate bath with a cation exchange membrane cell. The addition of 8 atom % iron to the Ni–W alloy ( Ni 78 Fe 8 W 14 ) removed surface microcracks on the deposits and increased the iron content, which was paralleled by an apparent increase in the tungsten content. To improve the microhardness, deposits were heat-treated at various temperatures. The maximum Vickers hardness value of 1350 was obtained after heat-treatment at 500 ° C . X-ray diffraction analysis revealed that the increasing annealing temperature induced both grain growth and precipitation of new phases, especially NiWO 4 . Transmission electron microscopy and selected area diffraction observations revealed that annealing at 500 ° C led to a significant hardening of the deposits due to the precipitation of new phases with nanosized grains. However, as the annealing temperature was increased above 500 ° C , the microhardness began to fall with increasing grain size.