Thermal stability of electrodeposited Ni-P alloys

Ni-P alloys were electrodeposited 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 9at% 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 17at% 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.