Effect of Laser Welding Speed on Grain Morphology and Tensile Property of TA15 Titanium Alloy Bottom-Locking Joint

Abstract

The laser welding of TA15 titanium alloy with the bottom-locking joints is carried out by TruDisk-12003 disc laser. In this paper, the microstructure and tensile properties of welded joints with different welding speeds are studied. The microstructure is observed by optical microscope. The tensile fracture morphology and chemical composition are analyzed by scanning electron microscope (SEM) and energy dispersive spectrometer (EDS) respectively. The experimental results show that the width of weld zone (WZ) is decreased significantly with the increasing of welding speed. The β columnar crystal shows respective morphology and growth direction in WZ under different welding speeds, meanwhile, the number of acicular martensite which is precipitated in columnar crystal also presents different. Besides, the aggregate growth zone of columnar crystal at the bottom of weld zone gets smaller with the increase of welding speed. The maximum tensile strength for the TA15 titanium alloy bottom-locking joint, which is fractured at weld joint, reaches 89% of the BM. Besides, the EDS results illustrate that the burning loss of stabilization element is inevitable.