Microstructure in the weld region in seam welded and resistance welded Zircaloy 4 tubing

The microstructure of tungsten inert gas (TIG)-arc welding and resistance welding in Zircaloy 4 tubing is described in relation to the phases present. Differences in microstructure between the weld zone and base tubing are discussed in terms of the phase transformations that take place during the very different thermal cycles occurring in both processes and a comparison between them is made. A feature of the weld region is the presence of a coarse grained Widmanstätten structure in the TIG welding while a martensitic-type structure or very fine Widmanstätten structure is present in resistance welding.