Microstructure and mechanical properties of friction stir welded pure Mo joints

Commercially pure Mo plates, 1.5 mm thick, were successfully friction stir welded using an Ir–Re alloy tool. This material has the highest melting point (2620 °C) of those that have been friction stir welded so far. The joints showed a refined microstructure in the stir zone and a slightly coarsened structure in the heat-affected zone, wherein the fracture took place in tensile tests. The joints can reach a maximum tensile strength equivalent to 86% of that of the base metal.