Influence of Impurities and Temperature on the Microstructure of Zircaloy-2 and Zircaloy-4 after the Beta → Alpha Phase Transformation

    Published: Jan 1987

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    The formation of the basketweave structure (BW) or the parallel plate (PP) structure after β quench is known to depend upon C, Si, and P content. Traces of other impurities, volatile at the melting point of zirconium but insoluble at lower temperatures, are the most efficient in changing the as-quenched microstructures. The effect of the β heat treatment temperature varies according to the nature of insoluble phases initiating the βα phase transformation. When Si is the main impurity, cooling down from 1050°C leads to a parallel plate structure, whereas β heat treatments performed at higher temperatures promote a basketweave structure. This change of microstructure has been attributed to the variation of silicon solubility in the β phase with temperature. Volatile impurities with a low solubility result in different behavior under similar heat treatment; cooling down from 1050°C leads to the basketweave structure and fast cooling from 1200°C gives a parallel plate structure depending on impurity level.


    Zircaloy, impurity content, phase transformation, microstructure, β, quenching, melting, zirconium silicide, zirconium chloride, zirconium carbide, zirconium phosphide

    Author Information:

    Charquet, D
    Senior Engineer and Assistant Vice-President R&D, Centre de Recherches de CEZUS, Ugine,

    Alheritiere, E
    Senior Engineer and Assistant Vice-President R&D, Centre de Recherches de CEZUS, Ugine,

    Paper ID: STP28126S

    Committee/Subcommittee: B10.02

    DOI: 10.1520/STP28126S

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