Study of the β→α variant selection for a zircaloy-4 rod heated to the β transus in presence or not of an axial tensile stress

This contribution focuses on the β→α variant selection observed for a Zircaloy-4 rod, heated to the β transus, in presence (or not) of an axial tensile stress. The microstructures and the local textures of the α inherited phase have been characterized with crystal orientation maps. A specific processing of the data has been applied to distinguish on the maps, the colonies belonging to the same β grain and to deduce the parent grain orientations. The β grains were mainly oriented around the 〈1 1 1〉∥AD fiber and had preferentially transformed into different α variants belonging to the 〈1 1.0〉∥AD fiber. This variant selection is responsible for the sharp texture of the Zircaloy-4 rod after a treatment in the β field. Applying a stress at heating, reduces the β texture sharpness as well as the β→α variant selection. The origin of the variant selection mechanism is discussed and a variant selection model, based on the elastic anisotropy of the parent phase is applied to predict the variants favored by the transformation.