J. A. Querin, J. Schneider, Mississippi State University, Mississippi State, MS
In this study, flat 0.250” thick Ti-6Al-4V panels were friction stir welded (FSWed) using weld tools with tapered pins. The five different pin geometries of the weld tools included: 0 degree (straight cylinder), 15 degree, 30 degree, 45 degree, and 60 degree angles on the frustum. All weld tools had a smooth 7 degree concave shoulder and were made from microwave sintered tungsten carbide. For each weld tool geometry, the FSW process parameters were optimized to eliminate internal defects. All the welds were produced in position control with a 2.5 degree lead angle using a butt joint configuration for the panels. The process parameters of spindle rpm and travel speed were varied, altering the hot working conditions imparted to the workpiece. Load cells on the FSWing machine allowed for the torque, the plunge force, and the plow force to be recorded during welding. Resulting mechanical properties were evaluated from tensile tests results of the FSW joints. Variations in the material flow were investigated by use of microstructural analysis including optical microscopy (OM), scanning electron microscopy (SEM), and orientation image mapping (OIM).
Summary: In this study, flat panels of Ti-6Al-4V were friction stir welded (FSWed) using weld tools with tapered pins. Five different pin geometries were used, including: 0°, 15°, 30°, 45°, and 60° taper angles. These welds were characterized to determine the affects of varying taper on the weld tool work piece interaction.
