Effect of heat input on microstructure, mechanical and corrosion properties of electron beam welded zircaloy-4 sheets

The present study reports the effect of heat input on the evolution of microstructure, mechanical properties, and corrosion behavior of electron beam butt welded zircaloy-4 sheet. Joints prepared with lower heat input demonstrated lower peak temperature and higher cooling rate that resulted in narrow fusion zone and heat-affected zone. Fine basket weave Widmanstätten type structure in fusion zone was observed at lower heat input, while at higher heat input, a large columnar grain with coarse parallel plate Widmanstätten type structure was observed. Traces of second phase particles Zr(Cr,Fe)2 were also found in the fusion zone. The tensile strength of all welds was better than the base metal, irrespective of heat inputs. However, the joint prepared with lower heat input demonstrated higher ductility compared to other joints. The dominant mechanism of corrosion was found to be pitting type and it was supposed to be caused by intermetallic precipitation. The extent of corrosion decreased with decrease in heat input. Adhesive wear was found to be the dominant mechanism of wear and the coefficient of friction decreased with the decrease in heat input.