부산대학교 도서관

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 laserpower is 1000 w, 1300 kw, 1600 kw respectively. The bottom weld width and the width of high temperature heat-affectedzone (HT-HAZ) increase significantly as laser power increase. The microstructure of the heat-affected zone (HAZ) is relativelycomplicated, mainly composed of secondary α, acicular α structure and β. The microstructure at the weld metal iscomprised of the martensite α′ and acicular α. The tensile strength, fracture morphology and chemical composition of thewelded 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 ductilefracture in the shape of a dimple. The tensile strength of welded joint decreases with the increase of laser power. Whenthe 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 is64.55%, 62.95% and 62.05% of the base material strength. EDS results show that Mo and V elements are the strengtheningelements, while the burning loss of Mo and V reduce the strength of the joint.