Friction stir welding of Nb-1Zr alloy

Nb-1Zr alloy plates were successfully friction stir welded with the W-Re alloy tool for the first time. Geometric dynamic recrystallization (GDRX), discontinuous dynamic recrystallization (DDRX), and continuous dynamic recrystallization (CDRX) processes were observed on the welded joints. In addition, three different zones appeared in the joint: the base metal (BM), the stir zone (SZ), and the thermo-mechanically affected zone (TMAZ). No heat-affected zone (HAZ) is observed in the joint. With their refined grain size after welding, both welded zones (SZ and TMAZ) appeared to have considerably increased hardness compared to BM.