Enhanced interdiffusion and bonding in Zr-4/Ti/Zr-4 joints diffusion-bonded after hydrogenation

Zr-4 alloys were hydrogenated by gaseous hydrogen charging and then diffusion bonded using pure Ti interlayers to maintain a low bonding temperature while obtaining high strength. The effects of the hydrogen content and holding time on Zr-4-xH alloys (x represents the hydrogen content in wt.%) and their joints were investigated. Results show that the added hydrogen enhances the diffusion behavior during bonding and the joint quality. The layer growth rates and interdiffusion coefficients at the Ti/Zr-4-xH interlayer were calculated using the empirical power function and the Boltzmann-Matano method to confirm the diffusion enhancement. The flow stress and Young's modulus were also measured, demonstrating the improvement in plasticity. Specifically, the diffusion layer thickness (14.5 mu m) and shear strength (353 MPa) of the joint (0.5 wt% hydrogen, bonded at 700 degrees C and 15 MPa for 60 min) were 16% and 178% higher than those in the case without hydrogenation, respectively. This pre-hydrogenation method reduces the bonding temperature and improves the joint strength, thus advancing the industrial application of Zr alloys.