Weld Bead Size, Microstructure and Corrosion Behavior of Zirconium Alloys Joints Welded by Pulsed Laser Spot Welding

摘要

Pulsed laser spot welding of intersection points of zirconium alloys straps was performed. Weld bead size, microstructure and the corrosion behavior of weld bead were investigated. With the increasing laser peak power or number of shots, the weld width of the beads increased, the protrusion decreased and the dimple increased with further increase in heat input. The fusion zone consisted of a mixture of alpha Zr and residual beta Zr phases. After annealing treatment, beta Nb and Zr(Fe, Nb)(2) second phase particles were precipitated inter- and intragranular of alpha Zr grains adequately. The oxide thickness of annealed weld bead was about 3.90 mu m, decreased by about 18.1% relative to the 4.76 mu m of as-welded specimen corroded at 400 A degrees C and 10.3 MPa for 20 days. The corrosion resistance of annealed specimen was better than that of as-welded specimen, since the second phase particles exerted better corrosion resistance, and the content of Nb in beta Zr and the fraction of beta Zr decreased after the annealing treatment.