Thermal stability of electrodeposited Ni-P alloys

Ni-P alloys were electrodeposited on etched flat copper substrate, from phosphorous acid solutions in order to study their thermostructural stability, thermal desorption, and dimensional modifications during heat treatments. The quantity of phosphorus codeposited is not a linear function of the bath phosphorous acid content. X-ray diffraction shows that three characteristic composition ranges can be defined. In the first, corresponding to a Ni-P solid solution containing up to 9 at.% of phosphorus, the microstructural refining is attended by a disappearance of the (100) preferential orientation. Simultaneously with this textural change, a slight adsorption of hydrogen is observed. Beyond 9 at.% of phosphorus, the microcrystallized alloys are preferentially oriented in the [111] direction, and the gradual amorphization of Ni-P alloys is attended by adsorption of a very high volume of hydrogen. Beyond 17 at.% of phosphorus, the alloys are amorphous and the amount of hydrogen included during the electrocrystallization is at its maximum. A large part of the hydrogen is desorbed before the crystallization temperature and less of it is desorbed during the crystallization.