Abstract
A welded Zr-2.5%Nb plate with a texture similar to that of a CANDU* nuclear reactor pressure tube has been studied to determine the texture variations in the fusion zone and the heat affected zone (HAZ). The texture of the HAZ is explained by preferential growth of (001)[110] grains in the high-temperature bcc phase, with subsequent variant selection on cooling to enhance the volume fraction of (0002) normals perpendicular to the line of the weld. The same texture is observed in the fusion zone along with a (001)[100] texture component arising from solidification. The textures of the fusion zone and HAZ are not expected to increase the susceptibility of the welded plate to delayed hydride cracking.
Highlights
The pressure tubes in CANDU nuclear reactors are made of the alloy Zr-2.5%Nb which has a low neutron capture cros section and good mechanical properties
In this paper we present the textures of the a phase of a welded Zr-2.5%Nb plate in the base material, in the fusion zone and in the heat affected zone (HAZ) where the microstructure exhibits strong grain coarsening
In the HAZ directly adjacent to the fusion zone, the temperature of the base material is raised close to the melting point so the zirconium is all transformed from the original hcp phase into the bcc phase
Summary
The pressure tubes in CANDU nuclear reactors are made of the alloy Zr-2.5%Nb which has a low neutron capture cros section and good mechanical properties. In the HAZ directly adjacent to the fusion zone, the temperature of the base material is raised close to the melting point so the zirconium is all transformed from the original hcp phase into the bcc phase. In the HAZ the (0002) pole figure clearly indicates there was a dominant (001)[110] texture component in the bcc phase at high temperature.
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