Properties of Ni1−xFex (0.1 < x < 0.9) and Invar (x = 0.64) alloys obtained by electrodeposition

Electrodeposition of Ni1−xFex (x = 0.1–0.9) films was carried out from a chloride plating solution containing saccharin as an organic additive at a constant current density (5 mA/cm2) and a controlled pH of 2.5. X-ray diffraction studies revealed the existence of an fcc, or γ phase, in the range of 10–58 wt.% Fe, a mixed fcc/bcc phase in the range of 59–60 wt.% Fe, and a bcc, or α phase in the range of 64–90 wt.% Fe. The saturation magnetization, Bs, of electrodeposited Ni1−xFex alloys at the room temperature was found to increase with the increase of Fe-content and follows the Slater–Pauling curve, but deviates from as-cast bulk NiFe alloys. The coefficient of thermal expansion, CTE, of electrodeposited alloys at room temperature also deviates from as-cast bulk NiFe alloys. Annealing of α-Ni36Fe64 alloy results in a martensitic α → γ phase transformation, which takes place between 300 and 400 °C. It was demonstrated that thermal treatment above 400 °C was necessary to obtain magnetic and mechanical properties similar to those to conventional Invar alloy. Annealing of α-Ni36Fe64 alloy at 700 °C brings about a decrease of Bs from 1.75 to 0.45 T. By controlling the annealing conditions of α → γ martensitic transformation, it is possible to adjust the CTE of Ni36Fe64 alloy over the broad limits from 2.7 to 8.7 × 10−6/°C.