Friction stir welding process microstructure and property of weld for Zr-Sn-Nb-Cr-Fe zirconium alloys

Process performance, microstructure and corrosion properties of friction stir welded (FSW) joints of Zr-Sn-Nb-Cr-Fe zirconium alloys were studied in the present paper. The results indicate that the recommended zirconium alloys FSW joints with good shape and no welding defects were obtained by W-25%Re stir tool under the conditions of 250 rpm rotational speed, 40 mm/min welding speed, 10 kN axial force and argon protection. In stir zone (SZ), the severe plastic deformation leads to dynamic recrystallization, diffusion of alloying element and grain refinement and grain size increases with the increase of rotational speed. As the same time, a large number of irregularly shaped second phase particles were precipitated at the grain boundaries. These FSW joints prepared by different welding parameters exhibited black, bright and dense oxide film after being corroded in neutral water at 360 ℃, 18.6 MPa for 72 hours. However, the corrosion resistance of FSW joints decreases with the increase of rotational speed.