Investigation of the Microstructure and Mechanical Characteristics of Disk Laser-Welded Ti-6Al-4V Alloy Joints

Laser beam welding of 2-mm-thick sheets of the Ti-6Al-4V alloy is reported in this paper. Different combinations of processing parameters (shielding gas, laser beam power, focal position, welding speed) were used. The laser welding parameters have been correlated with macrostructure and microstructure of welded joints, their microhardness, and to tensile properties of the welded material as well as the weld joints themselves. It has been determined that argon as a shielding gas is more preferable than helium. For the manufacturing of the weld joints with good penetration and geometry, at least a 42.75 J/mm of heat input into the material should be introduced. In this case, the weld joint has fine microstructure containing acicular martensite and small amount of remaining β-phase, and both the weld joint and the base material manifest good mechanical properties. Undesirable microstructural coarsening and deterioration of mechanical properties of welded material occur when that optimal heat input to the material is too much exceeded.