Gas Tungsten Arc Welding of Aluminum Alloys with Nanocomposite 4943 Filler Material
- Author(s): Bethea, John Franklin
- Advisor(s): Li, Xiaochun
- et al.
Aluminum alloy 4943, specifically developed for arc welding, offers higher tensile and yield strength than AA 4043 and AA 4643 while maintaining weldability characteristics such as fluidity, shrinkage, solidification range, and low weld cracking sensitivity. Thus, it has become a preferred filler material option for high quality, repeatable welds, especially for 6xxx series aluminum. However, the strength and applicability of aluminum alloy welded joints with AA 4943 filler material remains limited despite excellent weldability. Previous studies have shown the promise of introducing ceramic nanoparticles into the aluminum alloy filler material to enhance mechanical properties and avoid problems typically associated with aluminum welding, such as solidification cracking. This idea has been extrapolated to AA 4943, which can be modified to produce welds with nanocomposite filler material. Any perceived benefits would have implications for many industries, in particular bicycle manufacturing which commonly uses AA 6061 for frames.
By introducing TiB2 nanoparticles into AA 4943 to produce welds of popular aluminum alloys through gas tungsten arc welding (GTAW), the effects of this nanocomposite filler were studied through characterization methods including microhardness testing, microstructure determination, and tensile testing. Little to no enhancements to mechanical properties were observed for welds with AA 4943 TiB2 nanocomposite filler when compared to welds with AA 4943 reference filler. Large clusters of TiB2 nanoparticles were observed in the secondary phase of the nanocomposite AA 4943 following casting and also observed in the as-welded samples in the weld zone. These clusters may be hindering ductility and providing a brittle fracture surface, lowering ultimate tensile strength of the samples and offering no grain size refinements. Additional manufacturing methods for the nanocomposite filler, such as extrusion, may offer a solution to the TiB2 clustering effect and superior nanoparticle distribution.