Defects Analysis of Large Additive Manufacturing Beam of Titanium Alloy

After forming, TC4 Titanium alloy additive manufacturing beams were inspected for defects. Defect size and position were tested by ultrasonic inspection and samples were cut down by WEDM. Afterwards, samples were prepared for metallographic analysis. The types and morphology of defects were tested and analyzed by stereoscopy, OM, SEM and EDS analysis. Besides, the micro-morphology near defects was observed and the chemical composition of inclusions was tested by EDS. The results show that the hole defects of titanium alloy beams resulted from poor fusion, which was caused by the mismatch between overlap ratio and Z increment. The inclusion defects are oxide inclusions. The forming environment was polluted by oxygen, so the surface of high temperature molten drop reacted with oxygen, leading to oxide skins, which then were embedded in the beam body. Besides, the micro-structure near poor fusion areas was also influenced by oxygen, where α phase increased and oxygen-rich α layers formed.