Mechanism of the HIP bonding of Zircaloy-4 in the α-phase field

The HIP bonding of as-received annealed Zircaloy-4 sheet of relatively large grain size has been investigated at elevated temperatures (770–810 °C) in the α-phase field. Studies of plastic flow behaviour showed that the material had a constant strain rate sensitivity of flow stress, m∼0.2, (n∼5) over a wide range of strain rates. The activation energy over this temperature range was consistent with power law creep as the rate controlling process for deformation. Bonding studies at 800 °C showed that interface void closure occurred by constrained plastic collapse and diffusion. The progressive increase of plastic constraint during void closure led to a dominance of diffusion. When the constraint of inter-void ligaments was introduced into an earlier model, this gave an improved agreement between prediction and experiment for diffusion bonding (DB) of the α-phase.