Effect of creep and α-Zr ↔ (α + β)-Zr transition in Zr1Nb cladding on texture analyzed by neutron diffraction

Abstract Zr1Nb alloy tubes used as nuclear fuel cladding in VVER reactors were deformed by isothermal creep under a temperature comprised between 350 °C and 850 °C and constant tensile stress of 5–200 MPa in axial direction (AD). Deformation texture was analyzed by neutron diffraction. Two types of texture were found. For the final type of texture, the test temperature was the decisive factor. Within the temperature range up to 600 °C, the effect of creep or plastic deformation dominates and the texture changes continuously with increasing deformation. The influence of the ratio of wall thickness reduction to diameter reduction (Rw/Rd) on texture originated by plastic deformation by compression of seamless tubes made of elemental zirconium or Zircaloy described by Tenckhoff (2005), was verified for textures formed by creep of cladding tubes made of Zr1Nb alloy (E110) by constant tensile stress at the 350–600 °C range. At 700 °C temperature or higher, the texture was formed mainly by reversible α-Zr ↔ (α + β)-Zr phase transition of significant proportion of zirconium crystals and the formation of a new texture was observed: The highest pole density in the TD have been observed for the pyramid ( 1 0 1 ¯ 1 ) followed by the prism ( 1 0 1 ¯ 0 ), which can be the effect of { 1 1 2 ¯ 1 } 〈 1 ¯ 1 ¯ 2 6 〉 twining. The prism ( 1 1 2 ¯ 0 ) rotates preferentially perpendicular to AD, while the pole density of prism ( 1 0 1 ¯ 0 ) is markedly low.