THERMAL-STABILITY OF ELECTRODEPOSITED NI-P ALLOYS

Ni-P alloys were electrodeposited from phosphorous acid solutions in o rder to study their thermostructural stability, thermal desorption, an d dimensional modifications during heat treatments. The quantity of ph osphorus codeposited is not a linear function of the bath phosphorous acid content. X-ray diffraction shows that three characteristic compos ition ranges can be defined. In the first, corresponding to a Ni-P sol id solution containing up to 9 at% of phosphorus, the microstructural refining is attended by a disappearance of the (100) preferential orie ntation. Simultaneously with this textural change, a slight adsorption of hydrogen is observed. Beyond 9at% of phosphorus, the microcrystall ized alloys are preferentially oriented in the [111] direction, and th e gradual amorphization of NI-P alloys is attended by adsorption of a very high volume of hydrogen. Beyond 17at% of phosphorus, the alloys a re amorphous and the amount of hydrogen included during the electrocry stallization is at its maximum. A large part of the hydrogen is desorb ed before the crystallization temperature and less of it is desorbed d uring the crystallization.