Analysis of the hydride formation kinetics of Zry-4

• Published in: Journal of alloys and compounds Vol. 330; pp. 483 - 487
• Main Authors: Fernández, G.E, Meyer, G, Peretti, H.A
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 17.01.2002
• Subjects: Hydriding kinetics; Hydrogen embrittlement; Zry-4; Hydriding kinetics; Zry-4; Hydrogen embrittlement
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/S0925-8388(01)01622-X

One of the most critical points when studying the hydriding reaction of Zr-based alloys is to determine internal kinetics parameters (IKP) independent of sample geometry that allow to compare hydrogen embrittlement of different compounds or the same alloy with different properties, e.g. constituents, microstructure or texture. In this sense, the design of new experiments and the theoretical modelling of the microscopic mechanisms occurring during hydrogen absorption are fundamental. In this work, we study the hydrogen absorption kinetics during activation of Zry-4 massive samples of standard and modified composition. During the reaction and due to the difference in specific volume between Zr and its hydride, the sample disintegrates by consecutive peelings of thin microlayers of approximately 20 μm of partially reacted material. This peeling process, coupled with the hydride reaction, leads to a linear stage in the overall absorption kinetics related to a hydride front of δ-phase that develops and grows at constant velocity from the sample surface. The hydride front velocity was measured for different sample geometry in the temperature range from 200 to 400°C. The activation energy associated with the process of advancing front was 54 KJ/mol. The value of this velocity at a given temperature as well as the activation energy can be used as an appropriate IKP for simulation or comparisons among different Zr-based alloys. We also evaluate the changes in activation energy and hydride front velocity due to modifications in microstructure and for different compositions of the microalloying materials (Ni, Fe and Cr).