An investigation of effect of annealing at different temperatures on microstructures and bulk textures development in deformed Zircaloy-4

- Deformed Zircaloy-4 was subjected to annealing at 400°C, 450°C and 500°C.
- Annealing twins, and high dislocation density up to 450°C were observed.
- Maximum hardness was observed at 450°C for all the conditions.
- Optimum twin growth at 450°C impeded dislocation motion and led to higher hardness.
- Texture evolution was due to annealing twins combined with various slip activity.

In the present work, the effect of various annealing temperatures on the microstructural and textural evolution in deformed Zircaloy-4 has been investigated. Zircaloy-4 was subjected to a rolling reduction of 90% corresponding to a true strain of 2.3 along the ND - ED and ND - TD planes of the as-received Zircaloy-4 bar at room (298 K) and cryogenic (77 K) temperatures. Following this, the various deformed conditions of the samples were subjected to annealing treatment at various temperatures such as 400°C, 450°C and 500°C. The deformed samples were characterized by a high dislocation density and nano scale subgrains, which after annealing at various temperatures were marked with annealing twins of nano - size along with some other dislocation configuration. A higher dislocation density and hardness (258.54 ± 2.91 HV) values were observed after annealing the cryorolled alloy along the ND - TD plane at 450°C. This high cold work energy provided by cryorolling along the ND - TD plane, after annealing at 450°C produced an optimum twin growth, which impeded the dislocation motion and slightly increased the hardness along this plane. Finally, the textures evolved after annealing indicated the role of annealing twins combined with < a > prismatic, < c + a > pyramidal & basal glide activity.