Mechanical and Metallurgical Investigation on the Friction Stir Brazing of Ti-6Al-4V and 321 Stainless Steelusing the BAg-8 braze alloy

This study investigates the influences of friction stir brazing(FSB) parameters on microstructures and mechanical properties of Ti-6Al-4V/321 stainless steel joint. BAg-8filler metal was used as braze alloy. Experiments were carried out at 1500 and 2500 rpm for rotating speeds and 50 and 100 mm/min for advancing speeds. The bonds were characterized by optical microscopy(OM), scanning electron microscopy (SEM), X-Ray diffraction (XRD) and energy dispersive spectroscopy(SEM-EDS). Also shear test and microhardness were carried out as mechanical experiments.The results showed that suitable metallurgical bonding without any of crack were established. A number of intermetallic phases such as Ti-Cu, Ag-Fe, Ti-Fe and Fe–Cu–Ti have been identified. It showed that, increasing of rotating speed and decreasing of advancing speed, increasing the thickness of intermetallic layer. At this condition average of shear strength of joints were decreased and microhardness were increased. The surface after shear test indicated that fracture occurs due to intermetallic layers and in the form of inter granual. The best results obtained at 1500 rpm for rotating speed and 100mm/min for advancing speed.

Keywords:

Friction stir brazing , Interface , Intermetallic compounds , Ti-6Al-4V , 321 Stainless steel