Estudo da soldabilidade dissimilar das ligas TI-6al-4v e AA-7075-t6 através do processo GMAW derivativo

Abstract

The dissimilar welding of Ti-6Al-4V and Al-7075 T6 alloys was studied using a controlled short-circuit GMAW process through the STT® (Surface Tension Transfer) module, which regulates the transfer of molten metal droplets via surface tension. These alloys hold great significance in various industrial sectors, particularly in the aerospace and automotive industries, due to their physical and mechanical properties, especially their excellent strength-to-weight ratio. However, their joining through fusion welding processes presents challenges due to the differences in their physical, chemical, and thermal properties. Thus, the objective of this study was to evaluate the interaction between peak current, background current, and wire feed speed in the GMAW process using STT® technology, combined with the preheating of the titanium alloy. The goal was to identify an optimal parameter combination that would enable the dissimilar welding of these alloys without the formation of deleterious phases that could compromise the mechanical properties of the welded joint. The joint was welded using a single-bevel butt joint with a 0.5 mm root opening. The titanium plate was beveled at 30° and preheated to 180 °C. The filler metal used was ER-4047 wire. The research successfully achieved the welding of the joints, defining parameters that allowed for the fusion of the alloys without forming an intermetallic layer in the bonding zone. The application of preheating and the use of welding energy between 2.66 and 3.07 kJ/cm² were critical for this outcome. The optimized combination of welding parameters, together with the controlled droplet transfer in STT® mode and the preheated titanium plate condition, enabled the dissimilar Al-Ti alloy joining by diffusion, without the formation of an intermetallic layer. This breakthrough contradicts the assertions of Rathod and Kutsuna, who two decades ago suggested that, due to the physicochemical differences between these alloys and the associated metallurgical challenges, their practical fusion welding application was not feasible. The present study represents a significant innovation in the field, as the development of dissimilar weld interfaces without intermetallic layer formation has been one of the major challenges in the research on these alloy joints. Until now, no successful reports have been documented in the literature regarding the fusion welding of Al-7075 T6 and Ti-6Al-4V, highlighting the novelty and relevance of these results.