High-strength titanium alloy/steel butt joint produced via friction stir welding

For the first time, defect-free butt welds of titanium alloy/steel were successfully fabricated via friction stir welding. Joints were produced by employing rotation speed varied at 600 and 950 rpm with a constant travel speed of 47.5 mm/min. An increasing of rotation speed leads to thicken the intermetallic compound layer, coarsen the grain size and thus decrease the joint microhardness. Thanks to the solid-state joining process, only a thin FeTi layer was formed at the interface even rotation speed increased to 950 rpm. As a result, all obtained joints fractured at the base steel material. The work carried out clearly shows the good weldability of titanium alloy to steel via friction stir welding.