Effect of Laser Power on Tensile Performance of TA15 Laser-Welded Lock Bottom Joint

Abstract

Taking TA15 titanium alloy as the research object, laser welding experiments of are performed on the lock-bottom joints, and the microstructure and tensile performance of the joints are analyzed. The laser welding speed is constant and the laser power is 1000 w, 1300 kw, 1600 kw respectively. The bottom weld width and the width of high temperature heat-affected zone (HT-HAZ) increase significantly as laser power increase. The microstructure of the heat-affected zone (HAZ) is relatively complicated, mainly composed of secondary α, acicular α structure and β. The microstructure at the weld metal is comprised of the martensite α′ and acicular α. The tensile strength, fracture morphology and chemical composition of the welded joint are studied by tensile test, scanning electron microscope (SEM) and energy dispersive spectrometer (EDS) analysis techniques. The results show that all the specimens fractured near the heat-affected zone, and the fracture is a ductile fracture in the shape of a dimple. The tensile strength of welded joint decreases with the increase of laser power. When the laser power is 1.0 kw, 1.3 kw and 1.6 kw, the tensile strength is 723 MPa, 705 MPa and 695 MPa respectively, which is 64.55%, 62.95% and 62.05% of the base material strength. EDS results show that Mo and V elements are the strengthening elements, while the burning loss of Mo and V reduce the strength of the joint.