Tensile Behavior and Microstructural Characteristics of Friction Stir Welded Butt Joints of Titanium Alloys




Abstract: This study demonstrates mechanical and metallurgical characterization of friction stir welded (FSWed) three titanium alloys i.e., ATI-425, TIMET-54M, and Ti-6Al-4V with typical α and β phases in base material (BM) microstructure. Weld parameters consist of rotational and
traverse speeds. Defect free welds were obtained at 300 RPM and 100 mm/min. FSW produced Widmanstätten morphology in the weld nugget (WN) for all cases except Ti-6Al-4V, demonstrating the temperatures reaching par β transus in WN for ATI-425 and Timet-54M. Global tensile tests revealed that the fracture occurred in the WN, for ATI-425; in the
base material for TIMET-54M; and in the retreating side heat affected zone/thermo mechanically affected zone (HAZ/TMAZ) forTi-6Al-4V in this study. The HAZ and TMAZ for TIMET-54M, and Ti-6Al-4V consist of refined bimodal, and equiaxed α grains. HAZ, for ATI-425 results in refined equiaxed α infused with β. Hardness increased in WN for all cases;
presence of HAZ is marked by the drop in the hardness values because of recrystallized grains in HAZ.

Authors: Laxminarayana Pappula, Kapil Gangwar, Ashok Kumar Uppari, and Ramulu M

Keywords: Ti-Alloys, FSW, Microstructure, Tensile Test

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8 pages