Electron beam welding of dissimilar Titanium to aluminium: Interface microstructure and mechanical properties

Abstract

Welding of dissimilar metals, titanium–aluminium having wide differences in mechanical and thermal properties was highly challenging. In the present investigation, the electron beam welding method was used to join titanium alloy with pure aluminium. The results show that at the optimum parameter levels such as beam current of 6 mA, welding speed of 8 mm/s, and beam offset of 70:30 (Ti:Al) toward titanium, a defect-free joint with the higher mechanical strength of 120 MPa was achieved compared to the other combination of parameters. The percentage contribution of significant parameters was welding speed of 62%, and beam current of 25%. The scanning electron microscope was used to study the Ti–Al interface microstructure in detail. A significant increase in the micro-hardness in the weld zone was due to a change in titanium microstructure from equiaxed α-phase to acicular α and the formation of Ti-Al intermetallics in the fusion zone. X-ray diffraction analysis was used to analyze the phases present in the fusion zone. It was confirmed that there were mainly Al-Ti compounds like Al2Ti, Al3Ti, AlTi, AlTi2, Al11Ti5. These phases are harmful and contributed to higher hardness and brittleness in the fusion zone. At optimum conditions, a defect-free joint without intermetallics was obtained without an increase in hardness in the fusion zone.