Influence of filler wire on the microstructure and mechanical properties of laser beam welded Ti-6Al-4V butt-joints
Fedor Fomin, Volker Ventzke, Stefan Riekehr, Nikolai Kashaev
The purpose of the present work is to investigate the effects of filler wire on temperature distribution, microstructure and microtexture of Ti-6Al-4V butt-joints accomplished by laser beam welding (LBW). Experimental work involved measurements of temperature distribution during LBW, microhardness testing, metallographic analysis and investigation of local chemical composition. It has been determined that filler wire doesn’t significantly affect the temperature field and cooling rate during the LBW process. Although the shape of the welding beads completely changes in case of adding filler wire, any differences in microstructure and microtexture of the welds were not found. Significant drop downs of microhardness were observed in case of welding with filler wire. Possible reasons of such differences in microhardness profiles were discussed. It was concluded that the loss of alloying elements in the fusion zone is the main reason of different mechanical properties in the case of using Ti Grade 2 filler wire. A 3D transient finite elements (FE) model was developed to predict thermal processes taking place in the workpiece during LBW. There was a close correlation between the experimental data and simulation results, which increases the feasibility of FE simulation to predict the geometry and properties of LBW-beads. The results of the work provide additional understanding of the ways to optimize and improve laser assisted techniques of welding.
Keywords: Ti-6Al-4V, filler wire Titanium Grade 2, Laser Beam Welding (LBW), microstructure, temperature field, mechanical properties.