Structural Properties and Stability of Metastable Phases in the Zr-Nb System

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The lattice parameters of the bcc (b) and omega (W) phases occurring metastably in a series of Zr-rich Zr-Nb alloys have been determined at and above room temperature (TR) using neutron diffraction techniques. In the first place, the effect of temperature changes upon the lattice parameters of the b and W phases in alloys with 10 and 18 at.% Nb was monitored using neutron thermodiffraction. A method of analysis is applied to the data which involves a confrontation between the observed structural properties and an idealised -or ``reference'- behaviour (RB) which admits a simple mathematical description. A generalised form of Vegard's law is adopted as RB for the b phase, whereas a specific RB is proposed for the W structure. The experimental data are well accounted for by this interpretation scheme, leading to a picture of the isothermal reactions occurring at high temperature which involves the transfer of Nb from the W to the b phase. Finally, the neutron diffraction data on the W phase are combined with an electron microscopy study for the alloy with 10 at.% Nb aged at 773 K, which provides information on the composition of this phase and its evolution towards thermodynamic equilibrium.

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Periodical:

Materials Science Forum (Volumes 480-481)

Edited by:

A. Méndez-Vilas

Pages:

565-572

Citation:

G. Aurelio et al., "Structural Properties and Stability of Metastable Phases in the Zr-Nb System", Materials Science Forum, Vols. 480-481, pp. 565-572, 2005

Online since:

March 2005

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$38.00

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