The effect of heat treatment on laser-welding performance of additive manufactured Ti6Al4V sheets

In this study, the laser weldability of Ti6Al4V materials produced by the selective laser melting (SLM) method, which is an additive manufacturing method, and the effects of heat treatment applied to the welded material on the welding performance were investigated experimentally. Stress relief and heat treatment were applied to the materials joined by laser welding at 800 °C (below the α phase transformation temperature), 950 °C (between α and β phase transformation temperature), and 1080 °C (above the β phase transformation temperature). In addition, transverse and longitudinal welded joining techniques were also investigated to determine anisotropy in the produced parts. The mechanical properties in the laser-welded region were examined by hardness and tensile tests, and an optical microscope, scanning electron microscope (SEM), and X-ray diffraction (XRD) examined the changes in the microstructure. Grain growth was observed in the microstructure due to the increase in heat treatment temperature, and the tensile strength increased from 631.2 to 754.2 MPa in transverse bonding, while it increased from 648.1 to 761.9 MPa in longitudinal bonding. High hardness values due to Widmanstatten morphology were determined in the hardness test, especially after heat treatments at 950 and 1080 °C. It has been observed that the heat treatment increases the welding performance of the laser-welded material, and the best welding performance is obtained with a welding efficiency of 83.5% in the heat treatment at 1080 °C.