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Thermodynamics and Kinetics of Crystal-Amorphous Transformation in A1–x Bx Alloys During Reaction with Hydrogen

Published online by Cambridge University Press:  25 February 2011

X. L. Yeh ,
W. L. Johnson ,
J. Y. Tang ,
C. R. Shi  and
W. M. Keck
X. L. Yeh
Affiliation:
Laboratory for Engneering Materials, California Institute of Technology, Pasadena, CA. 91125, U. S. A.
W. L. Johnson
Affiliation:
Laboratory for Engneering Materials, California Institute of Technology, Pasadena, CA. 91125, U. S. A.
J. Y. Tang
Affiliation:
Nuclear Science Department, Fudan University, Shanghai, China
C. R. Shi
Affiliation:
Nuclear Research Institute, Lanzhou University, Lanzhou, China
W. M. Keck
Affiliation:
Laboratory for Engneering Materials, California Institute of Technology, Pasadena, CA. 91125, U. S. A.
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Abstract

The kinetics of amorphous phase formation in polycrystalline A1–xBx (A=Zr, Hf, B=Pd, Rh,.15<x<.25) alloys during reaction with hydrogen has been studied by x-ray diffraction, +19F nuclear reaction depth profiling, TEM and electron diffraction. The formation of the amorphous hydride phase is observed by TEM to begin at grain bounderies of the polycrystalline Zr1–xRhx much in the same manner that “melting” nucleates at grain boundaries. TEM micrographs further show that the phase boundary between the crystalline and amorphous phases remains sharp during the growth of the amorphous phase. Both x-ray diffraction and nuclear depth profiling studies suggest that the overall rate of transformation to the amorphous hydride phase is limited by the rate of hydrogen permeation through the sample surface.

Based on the present experiments and an analysis of the relevant free energy curves, we discuss the thermodynamic and kinetic aspects of this effect to explain why an amorphous phase is formed.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 58 , 1985 , 63
Copyright
Copyright © Materials Research Society 1986

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References

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