The effect of FexNby (x = 2,7 and y = 1,6) intermetallics on microstructure and mechanical properties of electron beam welded Nb-1Zr refractory alloy

In this study, weldability and mechanical properties of dissimilar joint between Nb-1Zr and 321 stainless steel produced by electron beam welding were investigated. The results indicated that the optimum parameters to make this dissimilar joint possible are the electron beam offset of 50–50 and the current of 13 mA. Because of high melting temperature of Nb relative to 321 stainless steel and also high thermal conductivity of Nb, the molten weld pool was drawn to 321 stainless steel side containing 85.1%Vol 321 stainless steel and 14.9%Vol Nb. Non uniform regions were observed in the weld zone which were due to melt turbulence and its rapid solidification. The Fe7Nb6 and Fe2Nb intermetallic compounds formed in various regions of the weld zone directly govern the mechanical properties and weldability of the weld. Tensile strength of the weld was 170 MPa which was equal to 60.5% of that in autogenous weld of Nb-1Zr alloy. Tensile strength of the autogenous weld of Nb-1Zr alloy was 281 MPa. According to the Rosenthal's equations and measurements of the weld section, the recrystallization temperature of the Nb-1Zr was identified 1810 °C in the EBW condition.