Effect of Heat Treatments on Tensile Fracture Behaviour of Ti-6Al-4V Alloy Friction Welds

Friction welding of Ti-6Al-4V alloy is gaining considerable interest in the biomedical field for various applications. Ti-6Al-4V alloy is used to make biomedical equipment for a variety of uses, such as orthopaedic implants, dental implants, cardiovascular devices, and surgical instruments. The outstanding strength-to-weight ratio and biocompatibility of this alloy make it highly suitable for medical applications. In the present investigation, Ti-6Al-4V alloy rods were subjected to rotary friction welding. Prior to welding, pre-heat treatments were conducted in α + β and β conditions, followed by stress relieving on the Ti-6Al-4V rods. Additionally, some rods underwent stress relieving after the welding process. After multiple experimental trials, it was determined that friction welding at a rotational speed of 1500 rpm and an upset force of 5kN yielded defect-free joints. With the exception of a small difference in intensities, the XRD pattern shows that all conditions are quite similar. The existence of martensite and α colonies indicates that the transformation is a mixed phase. The tensile fracture behaviour of Ti-6Al-4V alloy welds were influenced by heat treatment. In as-received and stress-relieved welds, various characteristics were observed below the fractured surface, including changes in grain orientation, the presence of micro-voids, and discontinuous β grain boundaries. The α + β weld and α + β weld with stress-relieving conditions displayed high-density micro-voids, secondary void development, blunt cracks, and voids at the cusp of β grain boundaries. In β welds crack at prior beta grain boundaries, micro-voids in prior beta grains and kinking of α/β lamellae were observed. In β weld with stress-relieving micro-voids at the prior beta grain boundary and coarse slip bands within the prior β grains were observed. Scanning electron microscopy provided evidence of correlation among all features. © 2023, The Institution of Engineers (India).