Laser welding of electron beam melted Ti-6Al-4V to wrought Ti-6Al-4V: Effect of welding angle on microstructure and mechanical properties

Abstract

Electron beam melting (EBM) is an established powder-bed additive manufacturing process for small-to-medium-sized components of Ti-6Al-4V. For further employing EBM on fabricating large-scale components, an effort has been made by joining EBM-built Ti-6Al-4V plates to wrought counterparts using laser welding, and the welding angles between EBM build direction and weld bead have been chosen as 0°, 30° and 45°. The influence of the welding angles on the microstructure, microhardness of base metals, fusion zone, and heat-affected zones, as well as the macro tensile test have been characterized. The microhardness of each zone is determined by the local microstructure, and the macro tensile properties largely depend on the EBM base metal due to the internal defects generated during the EBM process. The effect of welding angles on tensile strengths is not significant, while the elongation drops from 9.4% to 5.8% as the welding angle increases from 0° to 45°. The mechanism of stress during uniaxial tension on EBM base metal is discussed based on the stress state of columnar grains and the internal defects.