Microstructural and Textural Differences Induced by Water and Furnace Cooling in Commercially Pure Zr Annealed in the α plus β Region

In this work, a commercially pure Zr sheet with a typical bimodal basal texture was annealed in an alpha + beta region and then subjected to different coolings (in water and furnace). Microstructures and textures of both the as-received and the heat-treated specimens were investigated by electron channeling contrast imaging and electron backscatter diffraction techniques. Results show that a duplex microstructure consisting of untransformed bulk alpha grains and twinned martensitic plates is produced in the water-cooled specimen, which possesses a weakened texture compared to the initial one. For the specimen cooled in furnace, however, a uniform microstructure fully comprised of coarser equiaxed grains with a strengthened texture is obtained. Analyses reveal that the rapid cooling in water could suppress variant selection behaviors during beta -> alpha transformation and allow alpha plates with scattered orientations to be nucleated inside beta phases, contributing to the weakened texture. In contrast, during slow cooling in furnace, beta boundaries would act as preferred nucleation sites of alpha embryos, resulting in a strong variant selection that accounts for the intensified texture.