| Abstract Scope |
Titanium and its alloys, namely Ti-6Al-4V, are commonly utilized in aerospace applications because of their high strength-to-weight ratio, corrosion resistance, and elevated temperature performance. Additive manufacturing (AM) is experiencing rapid growth in industry. Gas tungsten arc welding direct energy deposition (GTAW-DED) is one method to produce AM Ti-6Al-4V components. Additively manufactured Ti-6Al-4V components and multi-pass Ti-6Al-4V weldments exhibit large columnar β grains that grow epitaxially and exhibit coarse texture. It is difficult to achieve comparable properties to wrought and forged components. Significant effort is spent to explore methods of microstructural refinement in Ti-6Al-4V components. Previous research into grain refinement methods in titanium fusion welding includes beam and arc pulsation, inter-layer deformation, and alloying additions such as boron, beryllium, silicon, and yttrium. This research is aimed at evaluating advanced pulse gas tungsten arc welding and inter-layer ultrasonic peening to mitigate the negative effects of multi-pass welding and AM on Ti-6Al-4V.
For this study, single-pass thick Ti-6Al-4V walls were deposited using GTAW and 0.045" Ti-6Al-4V wire on a matching Ti-6Al-4V substrate. The welding current was pulsed with varying conditions to explore the effects of amplitude and pulse frequency. Data acquisition of arc current and voltage was taken. Metallographic analysis was conducted transverse and longitudinal to the welding direction. Experimental testing found that advanced pulse waveforms had little improvement on mechanical properties and microstructure in Ti-6Al-4V weldments. The negative effects of epitaxial nucleation and growth were not obstructed. Inter-layer ultrasonic peening was investigated as an additional approach, with further exploration of its effects on microstructure ongoing. Future work will include a deeper study into ultrasonic peening parameters and the addition of inter-layer compressive rolling. |