Welding processes and microstructures of weld bead of Zr-Sn-Nb-Fe-Cr and Zr-Nb-Fe zirconium alloy

Zr-1.0Sn-0.50Nb-0.50Fe-0.14Cr and Zr-Nb-Fe alloys were the two new developed zirconium alloys which used in fuel assembly. In this paper, different welding parameters of the Zr-1.0Sn-0.50Nb-0.50Fe-0.14Crguide thimble welded toZr-1.30Nb-0.30Fe tab by using pressure resistance spot welding method were studied. The mechanical properties and microstructures of the optimum welding parameters of the weld bead were studied. The result showed that the shear strength and nugget size increased as the welding current increased and the welding force decreased. The Failure mode of the weld bead changed from junction surface fracture to button fracture as the welding current increased. The welding current was the key factors on the mechanical properties and microstructure. As the increasing of the electrode force, the welding shearing strength and the diameter of the welding core size decreased. Under the imbalance express cooling, the fusion zone consists of a mixture of α-Zr and β-Zr phases among which lamellar structure. The fine Fe₂(Nb_0.35, Zr_0.65) and Fe₂(Nb_0.3, Z_r0.7) second phases particles were precipitated inter and intergranular in the grains, so the mechanical and anti-water corrosion properties were improved.