Modified utilization of semi-sectioned tubes as filler coated with MWCNTs–TiO2 in TIG arc welding to recover fusion lost mechanical properties of the weldment

The loss of mechanical properties in heat treatable aluminum alloys categories during arc fusion welding processes is a critical issue, which limits the direct application in contrast to different post-treatments methods. This work involved a strategy for the novel and distinctive formation of fillers using 3-mm-diameter (AA6061) tubes having MWCNTs and TiO2 nanoparticles coating on the inner surface. A series of experiments were conducted using TIG welding to evaluate the effect of welding current and composition of inside coating (MWCNTs–TiO2) contents on welding strength. Three gradually increasing current values (160 A, 180 A and 200 A) were selected and tested against three combinations of nanocomposite coatings that include 1 wt% MWCNTs–TiO2, 1.5 wt% MWCNTs–TiO2 and 2 wt% MWCNTs–TiO2. Acceptable qualified bonding between nanocomposite and inside surface is utmost important before conducting the experiments, Tape Test (ASTM-D3359-09e2) was performed for the assessment of bonding conditions and led to qualitatively exceptional bonding conditions after applying vacuum heating cycle. Tensile test results have demonstrated a significant improvement of 34.20–45.65% strength using innovative nanocomposite coated semi-sectioned tube in comparison to tube fillers without coating. Meanwhile, a beneficial gradually forming W-shape microhardness profile in contrast to conventional U and V shape profiles was achieved at 1.5 and 2 wt% of MWCNTs, and the uplift of hardness in the WZ region up to 86.51% subjected to increase high MWCNTs contents in combination with the current. Therefore, it is concluded to be a virtuous strategy for reinforcing mechanism of weldments to encounter some fusion property loss in aluminum alloys.