Evolution of texture and intergranular stresses of αZr and minority phases in Zr-2.5Nb pressure tube through synchrotron X-ray diffraction

Abstract

This study investigates the impact of different processing steps on the crystallographic textureevolution of αZr and minority phases βZr and ωZr, and intergranular stresses as a function ofgrain orientation in a Zr2.5Nb pressure tube. This was done by analysis of diffraction datarecorded in the 1-ID line of the Advanced Photon Source for high energy X-Rays (~80Kev) intransmission geometry on three samples with different processing conditions: extruded, coldrolled and after autoclaving. The crystallographic texture of both αZr and βZr phases changesslightly after cold rolling, with the Burgers orientation relationship between the two phasesremaining intact. The texture of βZr and ωZr shows that βZr decomposition during thermaltreatment is sensitive to grain orientation. A new method was proposed to obtain the orientationdependence of the intergranular stresses from the experimental pole figures. Intergranularstresses in αZr grains were low after extrusion, but rolling significantly increased them, withvalues with magnitude as higher as 350 MPa and a strong dependence on grain orientation. Theautoclaving treatment leads to important stress relaxation, but the dependence on grainorientation remains. The βZr phase grains exhibit significant intergranular strains in bothextruded and cold-rolled conditions; the hydrostatic part was associated the presence of Nb insolid solution, with content of 20% and an orientation dependence of approximately ±1 at%.The deviatoric strain was attributed to intergranular stresses, with stresses below 80 MPa for theextruded sample and ranging from -600 to 400 MPa after cold rolling.