Microstructure Evolution during Friction Stir Welding of Mill-Annealed Ti-6Al-4V (Preprint)
AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH MATERIALS AND MANUFACTURING DIRECTORATE
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In this study, mill-annealed Ti-6Al-4V plates were successfully friction stir welded over a wide range of processing parameters using a tungsten - 1La2O3 tool. Two K-type thermocouples embedded in the tool indicated that approximately 25 pct. of the heat generated during welding was transferred out of the workpiece and into the tool. The thermocouple data, combined with observations of the microstructure, indicated that the stir zone of all welds exceeded the 946 transus. The microstructure and texture of two representative welds made just above and high above the beta transus were investigated with scanning electron microscopy and electron backscatter diffraction EBSD. The beta phase orientations were reconstructed with a fully automated technique from the ascollected alpha phase data through knowledge of the Burgers orientation relationship. The results suggest that the fine betagrains in the stir zone are formed from the base material ahead of the advancing tool by dissolution of secondary and primary alpha phase and there is no further recrystallization.
- Properties of Metals and Alloys
- Fabrication Metallurgy