Effect of Welding Conditions on Microstructural Evolution of Friction-Stir-Welded Ti-Cu Plate

Fusion welding of Ti-Cu is difficult because of big difference of melting points and formation of brittle intermetallic compounds. Friction stir welding is carried out by solid-state joining, thermo-mechanical stirring, and friction heat. Ti-Cu FSW dissimilar welding can supply a very sound joint area with a few intermetallic compounds. Optimized welding process conditions are essential to obtain suitable microstructure and mechanical properties of welded zones. Different welding speeds affect the evolution of microstructure and mechanical properties due to changes of input heat and internal stored deformation energy. The correlation of microstructure and mechanical properties of Ti-Cu welded zone according to welding speeds were investigated and analyzed. As the higher the welding speed, the lower the heat input and the lower the temperature rise. Ti-Cu 75 has the smallest grain size at 13.9 μm, but the optimum mechanical properties and the integrity of welding were shown in Ti-Cu 50.