Analysis of Bonding Interface in Diffusion Bonded R-SU304ULC/Ta/R-Ti-5Ta/Zr Joint

Study on Bonding of Ziroconium and Stainless Steel (Report 2)

Abstract

Microstructural analyses of the bonding interface in R-SUS304ULC/Ta/R-Ti-5Ta/Zr diffusion bonded joint were conducted in order to improve the embrittlement of the Ta/Zr interface. Diffusion bonding of R-SUS304ULC/Ta/R-Ti-5Ta/Zr was carried out at 1073-1373 K for 0-10 ks in vacuum. SEM and TEM observations revealed that the needle-like microstructure (transition zone) was formed at the Ta/R-Ti-5Ta and R-Ti-5Ta/Zr interface. Ta and α-Ti were identified in the transition zone at the Ta/R-Ti-5Ta interface, while the needle-like microstructure at the R-Ti-5Ta/Zr interface consisted of two kinds of α-(Zr, Ti) solid solution with different Ti compositions. The hardened area was located at the Ta/R-Ti-5Ta and R-Ti-5Ta/Zr interfaces, however, cracks didn't occur in the hardened zones. The growth of the transition zones could be expressed by the parabolic growth law during bonding operation.