Effect of friction time on mechanical and metallurgical properties of continuous drive friction welded Ti6Al4V/SUS321 joints

Dissimilar joint of Ti6Al4V titanium alloy and SUS321 stainless steel was fabricated by continuous drive friction welding. The effect of friction time on the mechanical properties was evaluated by hardness measurement and tensile test, while the interfacial microstructure and fracture morphologies were analyzed by scanning electron microscope, energy dispersive spectroscope and X-ray Diffraction. The results show that the tensile strength increases with friction time under the experimental conditions. And the maximum average strength 560MPa, which is 90.3% of the SUS321 base metal, is achieved at a friction time of 4s. For all samples, studied fracture occurred along the joint interface, where intermetallic compounds like FeTi, Fe₂Ti, Ni₃(Al, Ti) and Fe₃Ti₃O and many other phases were formed among elements from the two base metals. The width of intermetallic compounds zone increases with friction time up to 3μm, below which it is beneficial to make a strong metallurgical bond. However, the longer friction time leads to oversized flash on the Ti6Al4V side and overgrown intermetallic compounds. Finally the optimized friction time was discussed to be in the range of 2-4s, under which the sound joint with good reproducibility can be expected.