Strengthening or weakening texture intensity of Zr alloy by modifying cooling rates from α plus β region

A typically textured Zr alloy sheet was heat-treated in an alpha + beta region (at 950 degrees C) and then cooled at three different rates (in water, air and furnace). Microstructures and textures of various specimens were carefully characterized and analyzed by electron channeling contrast (ECC) imaging and electron backscatter diffraction (EBSD) techniques. Results show that rapid cooling in water leads to considerably weakened texture while slower cooling produces perfectly inherited (air cooling) or even intensified texture (furnace cooling). Microstructural examinations reveal that duplex microstructures consisting of fine intersecting plates (martensites) and bulk prior a grains are produced in the water-cooled specimen. Air cooling is also able to induce duplex microstructures with the plates corresponding to coarse parallel-plate Widmanstatten structures. Uniform microstructures of fully equiaxed grains are obtained in the slowest cooled specimen (in furnace). EBSD orientation analyses show that multiple a variants with scattered orientations can be produced inside each beta phase during water cooling, resulting in the weakened transformation texture. At slower cooling, however, alpha/beta phase boundaries act as preferred nucleation sites and then strong variant selection occurs, leading to textural inheritance or strengthening. (C) 2018 Elsevier B.V. All rights reserved.