Ds. Dossantos et Pev. Demiranda, THE USE OF ELECTROCHEMICAL HYDROGEN PERMEATION TECHNIQUES TO DETECT HYDRIDE PHASE-SEPARATION IN AMORPHOUS METALLIC ALLOYS, Journal of non-crystalline solids, 234, 1998, pp. 133-139
Samples of amorphous Fe40Ni38Mo4B18 and Ni81P19 alloys were submitted
to electrochemical hydrogen permeation tests, under cathodic charging
conditions, which resulted in elevated hydrogen fugacity. Two differen
t permeation techniques were used: the double-potentiostatic and the p
otentiostatic step methods. The main difference between these techniqu
es is the form of the resulting hydrogen concentration profile across
the sample thickness. The hydrogen permeation curves for the Ni81P19 s
amples, for both techniques, had shapes identical to the theoretical c
urves. The experimental curves for the Fe40Ni38Mo4B18 samples, however
, deviated from the theoretical curves. These deviations are attribute
d to the formation of a hydride phase due to the high hydrogen fugacit
y imposed during cathodic charging. The potential use of these electro
chemical hydrogen permeation techniques is demonstrated in the study o
f phase separation through the analysis of the growth of a new phase.
The diffusivity of hydrogen in the hydride formed in the Fe40Ni38Mo4B1
8 amorphous metallic alloy was found to be 5.7 +/- 0.3 x 10(-15) m(2)
s(-1) and the thickness of the hydride layer, formed during the double
-potentiostatic test, for a cathodic charging level of -2000 mV/SCE sa
turated calomel electrode (SCE) was found to be 18.9 +/- 0.5 mu m. (C)
1998 Published by Elsevier Science B.V. All rights reserved.